feat(stm32mp2): get chip ID

Add a function to get chip ID from SYSCFG peripheral.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I32b15fca00e52d31f253e02873ab01b804399658
diff --git a/plat/st/stm32mp2/platform.mk b/plat/st/stm32mp2/platform.mk
index 9614ed0..2b789c6 100644
--- a/plat/st/stm32mp2/platform.mk
+++ b/plat/st/stm32mp2/platform.mk
@@ -72,7 +72,8 @@
 PLAT_BL_COMMON_SOURCES		+=	plat/st/stm32mp2/stm32mp2_private.c
 
 PLAT_BL_COMMON_SOURCES		+=	drivers/st/bsec/bsec3.c					\
-					drivers/st/reset/stm32mp2_reset.c
+					drivers/st/reset/stm32mp2_reset.c			\
+					plat/st/stm32mp2/stm32mp2_syscfg.c
 
 PLAT_BL_COMMON_SOURCES		+=	drivers/st/clk/clk-stm32-core.c				\
 					drivers/st/clk/clk-stm32mp2.c