drm/radeon/kms: handle !force case in connector detect more gracefully
When force == false, we don't do load detection in the connector
detect functions. Unforunately, we also return the previous
connector state so we never get disconnect events for DVI-I, DVI-A,
or VGA. Save whether we detected the monitor via load detection
previously and use that to determine whether we return the previous
state or not.