rockchip: ringneck-px30: enable FIT verification in SPL

This enables FIT verification in SPL for its payload (bl31, u-boot.itb,
...). This makes PX30 Ringneck match what happens on other Theobroma
boards.

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

configs/ringneck-px30_defconfig

@@ -17,8 +17,10 @@ CONFIG_SYS_LOAD_ADDR=0x800800
 CONFIG_DEBUG_UART=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
+CONFIG_SPL_FIT_SIGNATURE=y
 CONFIG_SPL_LOAD_FIT=y
 CONFIG_BOOTSTD_FULL=y
+CONFIG_LEGACY_IMAGE_FORMAT=y
 CONFIG_DEFAULT_FDT_FILE="rockchip/px30-ringneck-haikou.dtb"
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
@@ -111,6 +113,7 @@ CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_EHCI_GENERIC=y
 CONFIG_SPL_TINY_MEMSET=y
 CONFIG_TPL_TINY_MEMSET=y
+# CONFIG_RSA is not set
 CONFIG_LZO=y
 CONFIG_ERRNO_STR=y
 # CONFIG_EFI_LOADER is not set