drm/fourcc: Add warning for bad bpp

drm/fourcc: Add warning for bad bpp

drm_format_info_bpp() cannot be used for formats which do not have an
integer bits-per-pixel in a pixel block.

E.g. DRM_FORMAT_P030's plane 0 has three 10-bit pixels (Y components),
and two padding bits, in a 4 byte block. That is 10.666... bits per
pixel when considering the whole 4 byte block, which is what
drm_format_info_bpp() does. Thus a driver that supports such formats
cannot use drm_format_info_bpp(),

It is a driver bug if this happens, but so handle wrong calls by
printing a warning and returning 0.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Acked-by: Simon Ser <contact@emersion.fr>
Link: https://patch.msgid.link/20260423-xilinx-formats-v10-1-c690c2b8ea89@ideasonboard.com
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>