avdevice/decklink: 10 Bit support for Decklink input device

Example to capture video clip at 1080i50 10 bit:
ffmpeg -bm_v210 1 -f decklink -i 'UltraStudio Mini Recorder@11' -acodec copy -vcodec copy output.avi

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