ARM: DRA7xx: Enable post-processing of FIT artifacts loaded by U-Boot

Enable the platform-specific post-processing of FIT-extracted blobs such
as Kernel, DTB, and initramfs on TI DRA7xx high-security (HS) devices
which will ultimately invoke a ROM-based API call that performs secure
processing such as blob authentication.
Signed-off-by: NAndreas Dannenberg <dannenberg@ti.com>
Signed-off-by: NAndrew F. Davis <afd@ti.com>
Reviewed-by: NLokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: NTom Rini <trini@konsulko.com>

configs/dra7xx_hs_evm_defconfig

@@ -65,3 +65,4 @@ CONFIG_PCF8575_GPIO=y
 CONFIG_DM_REGULATOR=y
 CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_CMD_REGULATOR=y
+CONFIG_FIT_IMAGE_POST_PROCESS=y