fourcc: add common 8-bit RGB without a mask
They correspond to libavutil AV_PIX_FMT_RGB8, AV_PIX_FMT_BGR8 and V4L2_PIX_FMT_RGB332/DRM_FORMAT_RGB332.
These formats don't have endianness problems...
Draft on top of !4224 (merged)
Edited by Steve Lhomme