vc1dec: Fix mv_f shuffling

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
vc1dec: Fix mv_f shuffling

Avoid a (confusing) memcpy()
Simpler code
Fixes a small number of artifacts in black_screen_VC-1.mkv
and several more artifacts in other videos

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
vc1dec: factorize picture pointer selection code

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>