cea861: add Short Video Descriptor block to the definitions, so we can parse out SVDs

Also correct definition of vendor specific block data (maximum payload is 28 bytes beyond the registration identifier)

include/linux/cea861.h

@@ -68,7 +68,16 @@ struct __packed cea861_vendor_specific_data_block {
 	struct cea861_data_block_header header;
 
 	u8 ieee_registration[3];
-	u8 data[30];
+	u8 data[28];
+};
+
+struct __packed cea861_video_data_block {
+	struct cea861_data_block_header header;
+
+	/* actual length in header, the index stops us from walking out of
+	 * spec but not out of bounds
+	 */
+	u8 svd[31];
 };