drm: only disable atomic modesetting when WLR_DRM_NO_ATOMIC == 1
drm: only disable atomic modesetting when WLR_DRM_NO_ATOMIC == 1

Don't allow any value of the env var to disable atomic mode setting.

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