feat(stm32mp1): update BACKUP_BOOT_MODE for STM32MP13

The backup register used on STM32MP15 to save the boot interface for
the next boot stage was 20. It is now saved in backup register 30
on STM32MP13.

Change-Id: Ibd051ff2eca7202184fa428ed57ecd4ae7388bd8
Signed-off-by: Yann Gautier <yann.gautier@st.com>

plat/st/stm32mp1/stm32mp1_private.c

@@ -37,7 +37,12 @@
 					 BOARD_ID_VARFG_SHIFT)
 #define BOARD_ID2BOM(_id)		((_id) & BOARD_ID_BOM_MASK)
 
+#if STM32MP13
+#define TAMP_BOOT_MODE_BACKUP_REG_ID	U(30)
+#endif
+#if STM32MP15
 #define TAMP_BOOT_MODE_BACKUP_REG_ID	U(20)
+#endif
 #define TAMP_BOOT_MODE_ITF_MASK		U(0x0000FF00)
 #define TAMP_BOOT_MODE_ITF_SHIFT	8