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/include/stm32mp2_private.h b/plat/st/stm32mp2/include/stm32mp2_private.h
index 2c44889..2ab5001 100644
--- a/plat/st/stm32mp2/include/stm32mp2_private.h
+++ b/plat/st/stm32mp2/include/stm32mp2_private.h
@@ -9,6 +9,8 @@
 
 void configure_mmu(void);
 
+uint32_t stm32mp_syscfg_get_chip_dev_id(void);
+
 /* Wrappers for OTP / BSEC functions */
 static inline uint32_t stm32_otp_probe(void)
 {