backend/drm: specify minimum config attributes
backend/drm: specify minimum config attributes

Since the format used by DRM is GBM_FORMAT_ARGB8888, we need at least a R, G, B
and A channel.

ascent12/wlroots,ascent12/wlroots,swaywm/wlroots,SirCmpwn/wlroots,swaywm/wlroots