arm: am4x: add U-Boot FIT signing and SPL image post-processing

Modify the SPL build procedure for AM437x high-security (HS) device
variants to create a secure u-boot_HS.img FIT blob that contains U-Boot
and DTB artifacts signed (and optionally encrypted) with a TI-specific
process based on the CONFIG_TI_SECURE_DEVICE config option and the
externally-provided image signing tool.

Also populate the corresponding FIT image post processing call to be
performed during SPL runtime.

Signed-off-by: Madan Srinivas <madans@ti.com>
Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/board/ti/am43xx/board.c b/board/ti/am43xx/board.c
index f005762..27c311e 100644
--- a/board/ti/am43xx/board.c
+++ b/board/ti/am43xx/board.c
@@ -13,6 +13,7 @@
 #include <asm/errno.h>
 #include <spl.h>
 #include <usb.h>
+#include <asm/omap_sec_common.h>
 #include <asm/arch/clock.h>
 #include <asm/arch/sys_proto.h>
 #include <asm/arch/mux.h>
@@ -862,3 +863,10 @@
 		return -1;
 }
 #endif
+
+#ifdef CONFIG_TI_SECURE_DEVICE
+void board_fit_image_post_process(void **p_image, size_t *p_size)
+{
+	secure_boot_verify_image(p_image, p_size);
+}
+#endif