plat/common: move arch-agnostic fallback functions to C file

When we add a new callback, we need to duplicate fallbacks among
plat/common/{aarch32,aarch64}/platform_helpers.S  This is tedious.

I created a new C file, then moved 3 functions:
  plat_error_handler
  bl2_plat_preload_setup
  plat_try_next_boot_source

They are called from C, so I do not see a good reason to implement
them in assembly.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Makefile

@@ -193,6 +193,7 @@ BL_COMMON_SOURCES	+=	common/bl_common.c			\
 				lib/${ARCH}/cache_helpers.S		\
 				lib/${ARCH}/misc_helpers.S		\
 				plat/common/plat_log_common.c		\
+				plat/common/platform_helpers_default.c	\
 				plat/common/${ARCH}/plat_common.c	\
 				plat/common/${ARCH}/platform_helpers.S	\
 				${COMPILER_RT_SRCS}			\

plat/common/aarch32/platform_helpers.S

 /*
- * Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -15,10 +15,7 @@
 	.weak	plat_disable_acp
 	.weak	bl1_plat_prepare_exit
 	.weak	platform_mem_init
-	.weak	plat_error_handler
 	.weak	plat_panic_handler
-	.weak	bl2_plat_preload_setup
-	.weak	plat_try_next_boot_source
 
 	/* -----------------------------------------------------
 	 * Placeholder function which should be redefined by
@@ -94,16 +91,6 @@ func bl1_plat_prepare_exit
 	bx	lr
 endfunc bl1_plat_prepare_exit
 
-	/* -----------------------------------------------------
-	 * void plat_error_handler(int err) __dead2;
-	 * Endless loop by default.
-	 * -----------------------------------------------------
-	 */
-func plat_error_handler
-	wfi
-	b	plat_error_handler
-endfunc plat_error_handler
-
 	/* -----------------------------------------------------
 	 * void plat_panic_handler(void) __dead2;
 	 * Endless loop by default.
@@ -112,23 +99,3 @@ endfunc plat_error_handler
 func plat_panic_handler
 	b	plat_panic_handler
 endfunc plat_panic_handler
-
-
-	/* -----------------------------------------------------
-	 * Placeholder function which should be redefined by
-	 * each platfrom.
-	 * -----------------------------------------------------
-	 */
-func bl2_plat_preload_setup
-	bx	lr
-endfunc bl2_plat_preload_setup
-
-	/* -----------------------------------------------------
-	 * Placeholder function which should be redefined by
-	 * each platfrom.
-	 * -----------------------------------------------------
-	 */
-func plat_try_next_boot_source
-	mov	r0, #0
-	bx	lr
-endfunc plat_try_next_boot_source

plat/common/aarch64/platform_helpers.S

 /*
- * Copyright (c) 2013-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -16,10 +16,7 @@
 	.weak	plat_reset_handler
 	.weak	plat_disable_acp
 	.weak	bl1_plat_prepare_exit
-	.weak	plat_error_handler
 	.weak	plat_panic_handler
-	.weak	bl2_plat_preload_setup
-	.weak	plat_try_next_boot_source
 
 #if !ENABLE_PLAT_COMPAT
 	.globl	platform_get_core_pos
@@ -158,16 +155,6 @@ func bl1_plat_prepare_exit
 	ret
 endfunc bl1_plat_prepare_exit
 
-	/* -----------------------------------------------------
-	 * void plat_error_handler(int err) __dead2;
-	 * Endless loop by default.
-	 * -----------------------------------------------------
-	 */
-func plat_error_handler
-	wfi
-	b	plat_error_handler
-endfunc plat_error_handler
-
 	/* -----------------------------------------------------
 	 * void plat_panic_handler(void) __dead2;
 	 * Endless loop by default.
@@ -177,22 +164,3 @@ func plat_panic_handler
 	wfi
 	b	plat_panic_handler
 endfunc plat_panic_handler
-
-	/* -----------------------------------------------------
-	 * Placeholder function which should be redefined by
-	 * each platfrom.
-	 * -----------------------------------------------------
-	 */
-func bl2_plat_preload_setup
-	ret
-endfunc bl2_plat_preload_setup
-
-	/* -----------------------------------------------------
-	 * Placeholder function which should be redefined by
-	 * each platfrom.
-	 * -----------------------------------------------------
-	 */
-func plat_try_next_boot_source
-	mov	x0, #0
-	ret
-endfunc plat_try_next_boot_source

plat/common/platform_helpers_default.c

+/*
+ * Copyright (c) 2013-2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arch_helpers.h>
+#include <platform.h>
+
+/*
+ * Placeholder functions which can be redefined by each platfrom.
+ */
+
+#pragma weak plat_error_handler
+#pragma weak bl2_plat_preload_setup
+#pragma weak plat_try_next_boot_source
+
+void __dead2 plat_error_handler(int err)
+{
+	while (1)
+		wfi();
+}
+
+void bl2_plat_preload_setup(void)
+{
+}
+
+int plat_try_next_boot_source(void)
+{
+	return 0;
+}