lavf/movenc: remove useless checks on AVOutputFormat

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
lavf/movenc: improve psp check

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Set bits_per_raw_sample when decoding mjpeg / ljpeg.

The ljpeg decoder also supports gray images with
8 - 15 bits per component.