stm32mp1: move check_header() to common code

This function can be used on several stm32mp devices, it is then moved in
plat/st/common/stm32mp_common.c.

Change-Id: I862debe39604410f71a9ddc28713026362e9ecda
Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/plat/st/common/include/stm32mp_common.h b/plat/st/common/include/stm32mp_common.h
index 3dd6c56..e20308e 100644
--- a/plat/st/common/include/stm32mp_common.h
+++ b/plat/st/common/include/stm32mp_common.h
@@ -10,6 +10,8 @@
 
 #include <stdbool.h>
 
+#include <platform_def.h>
+
 #include <arch_helpers.h>
 
 /* Functions to save and get boot context address given by ROM code */
@@ -94,4 +96,12 @@
 	return read_cntpct_el0() > expire;
 }
 
+/*
+ * Check that the STM32 header of a .stm32 binary image is valid
+ * @param header: pointer to the stm32 image header
+ * @param buffer: address of the binary image (payload)
+ * @return: 0 on success, negative value in case of error
+ */
+int stm32mp_check_header(boot_api_image_header_t *header, uintptr_t buffer);
+
 #endif /* STM32MP_COMMON_H */