drm/radeon: implement output csc property for DCE5+

[Dan Carpenter]

Hello Alex Deucher,

This is a semi-automatic email about new static checker warnings.

The patch 643b1f5629a3: "drm/radeon: implement output csc property 
for DCE5+" from Feb 23, 2015, leads to the following Smatch complaint:

drivers/gpu/drm/radeon/radeon_connectors.c:763 radeon_connector_set_property()
	 error: we previously assumed 'connector->encoder' could be null (see line 751)

drivers/gpu/drm/radeon/radeon_connectors.c
   750		if (property == rdev->mode_info.output_csc_property) {
   751			if (connector->encoder)
                            ^^^^^^^^^^^^^^^^^^
Check.

   752				radeon_encoder = to_radeon_encoder(connector->encoder);
   753			else {
   754				struct drm_connector_helper_funcs *connector_funcs = connector->helper_private;
   755				radeon_encoder = to_radeon_encoder(connector_funcs->best_encoder(connector));
   756			}
   757	
   758			if (radeon_encoder->output_csc == val)
   759				return 0;
   760	
   761			radeon_encoder->output_csc = val;
   762	
   763			if (connector->encoder->crtc) {
                            ^^^^^^^^^^^^^^^^^^
Unchecked dereference.

   764				struct drm_crtc *crtc  = connector->encoder->crtc;
   765				struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;

regards,
dan carpenter