codecparsers: remove ignored increment of return

'return val++;' returns the value before it is incremented because the post
increment happens after the statement. Removing the unused increment.

https://bugzilla.gnome.org/show_bug.cgi?id=739345

gst-libs/gst/codecparsers/gstmpeg4parser.c

@@ -347,7 +347,7 @@ compute_resync_marker_size (const GstMpeg4VideoObjectPlane * vop,
     }
   }
 
-  return off++;                 /* Take the following 1 into account */
+  return off;
 }
 
 /**