edid: Add an edid_check_checksum() helper function

Add a helper function to check the checksum of an EDID data block.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Anatolij Gustschin <agust@denx.de>

include/edid.h

@@ -245,6 +245,15 @@ void edid_print_info(struct edid1_info *edid_info);
  */
 int edid_check_info(struct edid1_info *info);
 
+/**
+ * Check checksum of a 128 bytes EDID data block
+ *
+ * @param edid_block	EDID block data
+ *
+ * @return 0 on success, or a negative errno on error
+ */
+int edid_check_checksum(u8 *edid_block);
+
 /**
  * Get the horizontal and vertical rate ranges of the monitor.
  *