stm32mp1: platform.mk: generate linker script with fixed name

The linker script has no board-specific information that necessitates it
having a name derived from the board name. Give it a fixed name, so we
can later reuse the same linker script for multiple boards.

Change-Id: Ie6650f00389f4ab8577ae82a36c620af9c64101e
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

plat/st/stm32mp1/platform.mk

@@ -153,7 +153,7 @@ STM32_DT_BASENAME	:=	$(DTB_FILE_NAME:.dtb=)
 STM32_TF_STM32		:=	${BUILD_PLAT}/tf-a-${STM32_DT_BASENAME}.stm32
 STM32_TF_BINARY		:=	$(STM32_TF_STM32:.stm32=.bin)
 STM32_TF_MAPFILE	:=	$(STM32_TF_STM32:.stm32=.map)
-STM32_TF_LINKERFILE	:=	$(STM32_TF_STM32:.stm32=.ld)
+STM32_TF_LINKERFILE	:=	${BUILD_PLAT}/stm32mp1.ld
 STM32_TF_ELF		:=	$(STM32_TF_STM32:.stm32=.elf)
 STM32_TF_DTBFILE	:=      ${BUILD_PLAT}/fdts/${DTB_FILE_NAME}
 STM32_TF_OBJS		:=	${BUILD_PLAT}/stm32mp1.o