drm: Fill depth/bits_per_pixel for C8 format

commit c51a6bc5f6d328926a9a4a1247c5030faf190a80 upstream.

Set depth/bits_per_pixel to 8 for C8 format.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>