platforms/drm: Port away from gbm_format_get_name()
gbm_format_get_name() is available in Mesa 19 and later, but some distros that ship Plasma 5.22 still have only Mesa 18.3.
gbm_format_get_name() is available in Mesa 19 and later, but some distros that ship Plasma 5.22 still have only Mesa 18.3.