PSCI: Pool platform_mem_init() in common ARM platforms code

Now that the FVP mailbox is no longer zeroed, the function
platform_mem_init() does nothing both on FVP and on Juno. Therefore,
this patch pools it as the default implementation on ARM platforms.

Change-Id: I007220f4531f15e8b602c3368a1129a5e3a38d91

plat/arm/board/fvp/aarch64/fvp_helpers.S

@@ -38,7 +38,6 @@
 
 	.globl	plat_secondary_cold_boot_setup
 	.globl	plat_get_my_entrypoint
-	.globl	platform_mem_init
 	.globl	plat_is_my_cpu_primary
 
 	.macro	fvp_choose_gicmmap  param1, param2, x_tmp, w_tmp, res
@@ -156,18 +155,6 @@ _panic:
 endfunc plat_get_my_entrypoint
 
 
-	/* ---------------------------------------------------------------------
-	 * void platform_mem_init (void);
-	 *
-	 * Nothing to do on FVP, the Trusted SRAM is available straight away
-	 * after reset.
-	 * ---------------------------------------------------------------------
-	 */
-func platform_mem_init
-	ret
-endfunc platform_mem_init
-
-
 func plat_is_my_cpu_primary
 	mrs	x0, mpidr_el1
 	and	x0, x0, #(MPIDR_CLUSTER_MASK | MPIDR_CPU_MASK)

plat/arm/common/aarch64/arm_helpers.S

@@ -34,6 +34,7 @@
 	.weak	plat_my_core_pos
 	.globl	plat_crash_console_init
 	.globl	plat_crash_console_putc
+	.globl	platform_mem_init
 
 
 	/* -----------------------------------------------------
@@ -86,3 +87,12 @@ func plat_crash_console_putc
 	mov_imm	x1, PLAT_ARM_CRASH_UART_BASE
 	b	console_core_putc
 endfunc plat_crash_console_putc
+
+	/* ---------------------------------------------------------------------
+	 * We don't need to carry out any memory initialization on ARM
+	 * platforms. The Secure RAM is accessible straight away.
+	 * ---------------------------------------------------------------------
+	 */
+func platform_mem_init
+	ret
+endfunc platform_mem_init

plat/arm/css/common/aarch64/css_helpers.S

@@ -34,7 +34,6 @@
 
 	.weak	plat_secondary_cold_boot_setup
 	.weak	plat_get_my_entrypoint
-	.weak	platform_mem_init
 	.globl	plat_arm_calc_core_pos
 	.weak	plat_is_my_cpu_primary
 
@@ -89,17 +88,6 @@ func plat_arm_calc_core_pos
 	ret
 endfunc plat_arm_calc_core_pos
 
-	/* -----------------------------------------------------
-	 * void platform_mem_init(void);
-	 *
-	 * We don't need to carry out any memory initialization
-	 * on CSS platforms. The Secure RAM is accessible straight away.
-	 * -----------------------------------------------------
-	 */
-func platform_mem_init
-	ret
-endfunc platform_mem_init
-
 	/* -----------------------------------------------------
 	 * unsigned int plat_is_my_cpu_primary (void);
 	 *