Fix loop filter with CAVLC 8x8dct.
Fixes at least:
FRExt/HPCV_BRCM_A.264
FRExt/HVLCFI0_Sony_B.264
FRExt/HVLCPFF0_Sony_B.264
H264_artifacts_motion.h264

Originally committed as revision 14373 to svn://svn.ffmpeg.org/ffmpeg/trunk
