When checking pix_fmt mapping, some bitstreams are mapped to an
incorrect pix_fmt instead of being rejected (ENOSYS).
Actually, such bitstreams are not supported (FFmpeg encoder does not
produce such bitstream, such bitstream may come only from another
encoder for the moment).

- JPEG 2000 RCT 11/13/15/16 bit depths are mapped to a 8-bit FFmpeg
pix_fmt (e.g. bgr0), which is not expected.
- JPEG 2000 RCT 9/10/12/14 bit depths with alpha are mapped to a
FFmpeg pix_fmt without alpha (e.g. AV_PIX_FMT_GBRP9 for 9-bit with
alpha), which is not expected.

The order for choosing the pix_fmt is changed to the one used by YCbCr
selection (<=8 bit first).
" && !f->transparency" is added to the other lines.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>