hevc: report more precise progress

There's a lag of one CTB line for SAO behind deblocking filter, except for
last line. However, once SAO has been completed on a line, all its pixels,
i.e. up to y+ctb_size are filtered and ready to be used as reference.

Without SAO, when deblocking filter finishes a CTB line, only the bottom
bottom 4 pixels may be filtered when next CTB is process by the deblocing.

The await_progess for hevc then checks whether the bottom pixels of a PU
requires access beyond that point, so the reporting should effectively
report up to the the above limits.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
hevc: cleaning up SSE2 and SSSE3 deblocking filters

Signed-off-by: Mickaël Raulet <mraulet@insa-rennes.fr>
hevc: cleanups in SSE2 and SSSE3 loop filters

- use of paddw instead of psllw

Signed-off-by: Mickaël Raulet <mraulet@insa-rennes.fr>
Merge branch 'rext' of https://github.com/OpenHEVC/FFmpeg into rext