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/common/spl/spl_mmc.c b/common/spl/spl_mmc.c
index 8d588d1..360c754 100644
--- a/common/spl/spl_mmc.c
+++ b/common/spl/spl_mmc.c
@@ -23,8 +23,12 @@
 {
 	u32 image_size_sectors;
 	unsigned long count;
+	int ret;
+
+	ret = spl_parse_image_header(header);
+	if (ret)
+		return ret;
 
-	spl_parse_image_header(header);
 	/* convert size to sectors - round up */
 	image_size_sectors = (spl_image.size + mmc->read_bl_len - 1) /
 			     mmc->read_bl_len;