Limit output sample to 0..maxval, fixes decoding of T16E0.JLS

Originally committed as revision 6908 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/jpeg_ls.c

@@ -384,6 +384,7 @@ static inline void ls_decode_line(JLSState *state, MJpegDecodeContext *s, void *
             pred = clip(pred, 0, state->maxval);
         }
 
+        pred &= state->maxval;
         W(dst, x, pred);
         x += stride;
     }