powerpc/mpc85xx: socrates: enable signed fitImages

allow only to boot signed fitimages (and signed u-boot
scripts).

Signed-off-by: Heiko Schocher <hs@denx.de>
diff --git a/configs/socrates_defconfig b/configs/socrates_defconfig
index d4c08f1..e03c971 100644
--- a/configs/socrates_defconfig
+++ b/configs/socrates_defconfig
@@ -16,7 +16,9 @@
 CONFIG_ENABLE_36BIT_PHYS=y
 CONFIG_SYS_MONITOR_LEN=786432
 CONFIG_FIT=y
+CONFIG_FIT_SIGNATURE=y
 CONFIG_FIT_VERBOSE=y
+CONFIG_LEGACY_IMAGE_FORMAT=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_SYS_MONITOR_BASE=0xFFF40000
 CONFIG_BOOTDELAY=1