vaapipostproc: prevent advanced-deinterlacing of non-native video formats.

vaapipostproc: prevent advanced-deinterlacing of non-native video formats.

This is a workaround to deal with the va-intel-driver for non-native
formats while doing advanced deinterlacing. The format of reference surfaces must
be same as the format used by the driver internally for motion adaptive
deinterlacing and motion compensated deinterlacing.

A permanent solution could be to do the color space conversion internally
for reference surfaces.

https://bugzilla.gnome.org/show_bug.cgi?id=730925

Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>