vpp: cache calculation of AVS coefficients.

If scaling parameters don't change, i.e. if the same scaling algorithm
and factors are used, there is no point in calculating the filter
coefficients again. So, just cache them into the existing AVS context.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
vpp: drop internal postprocessing (I965_PP_xxx) flags.

Exclusively use VA-API defined video processing flags, instead of yet
redefining another set with limited use. This means that we can use
scaling, colorspace and picture structure flags as is, without an extra
layer of conversion.

Drop I965_PP_FLAG_MCDI (motion compensated deinterlacing), which was
never set. Dropped the associated dead code, which was never used. And,
anyway, advanced deinterlacing modes shall go through the explcit VPP
interfaces.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
vpp: enable advanced video scaling in VPP pipelines too.

Honour advanced video scaling. i.e. propagate vaPutSurface() scaling
flags, but also VPP filter flags. Also enable the sharp 8x8 filter for
high-quality scaling options, while adaptive video scaling is disabled
(bypassed) for now.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>