arm: stm32mp1: Implement ECDSA signature verification

The STM32MP ROM provides several service. One of them is the ability
to verify ecdsa256 signatures. Hook the ROM API into the ECDSA uclass.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/arch/arm/mach-stm32mp/Makefile b/arch/arm/mach-stm32mp/Makefile
index 879c196..391b47c 100644
--- a/arch/arm/mach-stm32mp/Makefile
+++ b/arch/arm/mach-stm32mp/Makefile
@@ -11,6 +11,7 @@
 ifdef CONFIG_SPL_BUILD
 obj-y += spl.o
 obj-y += tzc400.o
+obj-$(CONFIG_STM32_ECDSA_VERIFY) += ecdsa_romapi.o
 else
 obj-y += cmd_stm32prog/
 obj-$(CONFIG_CMD_STM32KEY) += cmd_stm32key.o