Overall looks good, but it is a bit repetitive to copy & paste this in all
drivers. It'd be nice to provide a core helper to do this, and then drivers
can just set format_mod_supported to the helper if they don't have more
involved logic. Thoughts?
See drm_plane_check_pixel_format, where the logic is already implemented.
Alternatively… We can just support a missing format_mod_supported in
create_in_format_blob. This sounds like this was the original intention of
db1689aa61bd ("drm: Create a format/modifier blob") and
drm_plane_check_pixel_format.
