Revert "stm : fix error on b_u585i_iot02a with TF-Mv2.1.0"

This reverts commit 8bc7403. (cherry picked from commit beb096e)

Author: tomi-font

platform/ext/target/stm/b_u585i_iot02a/partition/flash_layout.h

@@ -83,7 +83,7 @@
 
 /* area for BL2 code protected by hdp */
 #define FLASH_AREA_BL2_OFFSET (FLASH_AREA_PERSO_OFFSET+FLASH_AREA_PERSO_SIZE )
-#define FLASH_AREA_BL2_SIZE (0x20000)
+#define FLASH_AREA_BL2_SIZE (0x16000)
 /* HDP area end at this address */
 #define FLASH_BL2_HDP_END (FLASH_AREA_BL2_OFFSET+FLASH_AREA_BL2_SIZE-1)
 /* area for BL2 code not protected by hdp */