firmware-utils: bcm4908img: fix extracting cferom

Fix offset to extract proper data when image contains vendor header.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit dcbde11af1)

tools/firmware-utils/src/bcm4908img.c

@@ -580,7 +580,7 @@ static int bcm4908img_extract(int argc, char **argv) {
 	}
 
 	if (!strcmp(type, "cferom")) {
-		offset = 0;
+		offset = info.cferom_offset;
 		length = info.bootfs_offset - offset;
 		if (!length) {
 			err = -ENOENT;