drm: call connector dpms fxn, when setting config

Call connector->funcs->dpms(DPMS_ON) rather than just setting
connector->dpms = DPMS_ON.  This ensures that if the connector
has something to do to enable the output (rather than just using
drm_helper_connector_dpms helper directly), that this happens
at bootup.  This solves an issue with connectors not getting
enabled from fbcon_init() when the driver is loaded.

Signed-off-by: Rob Clark <rob@ti.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>