libopenjpegenc: add support for pix fmt gbrp (8-16 bit)

Signed-off-by: Michael Bradshaw <mjbshaw@gmail.com>
libopenjpegenc: simplify switch statement

Signed-off-by: Michael Bradshaw <mjbshaw@gmail.com>
Merge remote-tracking branch 'mjbshaw/master'

* mjbshaw/master:
  libopenjpegenc: simplify switch statement
  libopenjpegenc: add support for pix fmt gbrp (8-16 bit)

Merged-by: Michael Niedermayer <michaelni@gmx.at>