drm: Add R10 and R12 FourCC

Add FourCCs for 10- and 12-bit red formats with padding to 16 bits.
They correspond to the V4L2 10- and 12-bit greyscale (V4L2_PIX_FMT_Y10
and V4L2_PIX_FMT_Y12) formats, as well as the Bayer formats with the
same bit depth (V4L2_PIX_FMT_SBGGR{10,12} and all other Bayer pattern
permutations).

These formats are not used by any kernel driver at this point, but need
to be exposed to applications by libcamera, which uses DRM FourCCs for
pixel formats.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211027233140.12268-1-laurent.pinchart@ideasonboard.com