SPL: Add support for checking board / BootROM specific image types

Commit 9baab60b8054 ("SPL: Add support for parsing board / BootROM specific
image types") added support for loading board specific image types.

This commit adds support for a new weak function spl_parse_board_header()
which is called after loading boot image. Board may implement this function
for checking if loaded board specific image is valid.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/common/spl/spl.c b/common/spl/spl.c
index 653e71f..54f9178 100644
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -589,6 +589,12 @@
 	return NULL;
 }
 
+__weak int spl_check_board_image(struct spl_image_info *spl_image,
+				 const struct spl_boot_device *bootdev)
+{
+	return 0;
+}
+
 static int spl_load_image(struct spl_image_info *spl_image,
 			  struct spl_image_loader *loader)
 {
@@ -610,6 +616,9 @@
 		}
 	}
 #endif
+	if (!ret)
+		ret = spl_check_board_image(spl_image, &bootdev);
+
 	return ret;
 }