boot_fit: Create helper functions that can be used to select DTB out of FIT

Some platforms may append a FIT image to the U-boot image. This function
aids in parsing the FIT image and selecting the correct DTB at runtime.

Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

include/boot_fit.h

@@ -0,0 +1,9 @@
+/*
+ * Copyright (C) 2017 Texas Instruments
+ * Written by Franklin Cooper Jr. <fcooper@ti.com>
+ *
+ * SPDX-License-Identifier:     GPL-2.0+
+ */
+
+int fdt_offset(void *fit);
+void *locate_dtb_in_fit(void *fit);