Current settings for video capture rgb-2-yuv is BT.601(studio swing),
but JFIF uses BT.601(full swing) to deocde. This mismatch will lead
to incorrect color. For example, input RGB value, (0, 0, 255), will
become (16, 16, 235) after jpg decoded.

Add an enum, aspeed_video_capture_format, to define VR008[7:6]
capture format and correct default settings for video capture to fix
the problem.

VR008[7:6] decides the data format for video capture as below:
* 00: CCIR601 studio swing compliant YUV format
* 01: CCIR601 full swing compliant YUV format
* 10: RGB format
* 11: Gray color mode
Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>