SPL: Let spl_parse_image_header() return value

Allow the spl_parse_image_header() to return value. This is convenient
for controlling the SPL boot flow if the loaded image is corrupted.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Peng Fan <van.freenix@gmail.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Tom Rini <trini@konsulko.com>
diff --git a/include/spl.h b/include/spl.h
index de4f70a..7edfab4 100644
--- a/include/spl.h
+++ b/include/spl.h
@@ -56,7 +56,7 @@
 u32 spl_boot_device(void);
 u32 spl_boot_mode(void);
 void spl_set_header_raw_uboot(void);
-void spl_parse_image_header(const struct image_header *header);
+int spl_parse_image_header(const struct image_header *header);
 void spl_board_prepare_for_linux(void);
 void __noreturn jump_to_image_linux(void *arg);
 int spl_start_uboot(void);