This is the default attachment, unbound gpu screens get
attached to the 0 protocol screen.
detach on hotunplug.
v2: detach after tearing down crtc/outputs.
Reviewed-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>