Add a hwdevice type for use with V4L2 Request API stateless decoding.
AVV4L2RequestFramesContext is expected to be filled with a V4L2 coded
pixel format and optional codec-specific extended controls before an
AVHWFramesContext is initialized.
Once initialized AVV4L2RequestFramesContextInternal describe the opened
V4L2 stateless decoder session, with details about media/video file
descriptors, formats of CAPTURE/OUTPUT queues and buffer pools for
creating CAPTURE/OUTPUT buffers.
AVHWFramesContext.pool defaults to create frame descriptors around a
CAPTURE buffer, and frames are returned with AVFrame.data[0] pointing
to a AVDRMFrameDescriptor and AVFrame.data[1] the CAPTURE buffer index.
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
