stm32mp1: use internal MAKE_LD macro to generate stm32 linker files

The previous proprietary version was not correctly handling dependencies.
Using MAKE_LD from make_helpers files now correctly handles that.
The generated linker script is the same as before.

Change-Id: Iccfd8dc3fffa7a33e73b184b72e0dfd5d26bc9c9
Signed-off-by: Yann Gautier <yann.gautier@st.com>

plat/st/stm32mp1/platform.mk

 #
-# Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -210,9 +210,7 @@ ${BUILD_PLAT}/stm32mp1-%.o:	${BUILD_PLAT}/fdts/%.dtb plat/st/stm32mp1/stm32mp1.S
 				-DDTB_BIN_PATH=\"$<\" \
 				-c plat/st/stm32mp1/stm32mp1.S -o $@
 
-${STM32_TF_LINKERFILE}:	plat/st/stm32mp1/stm32mp1.ld.S ${BUILD_PLAT}
-			@echo "  LDS     $<"
-			${Q}${AS} ${ASFLAGS} ${TF_CFLAGS} -P -E $< -o $@
+$(eval $(call MAKE_LD,${STM32_TF_LINKERFILE},plat/st/stm32mp1/stm32mp1.ld.S,2))
 
 tf-a-%.elf:		stm32mp1-%.o ${STM32_TF_LINKERFILE}
 			@echo "  LDS     $<"