drm: fix drm_mode_getconnector() locking imbalance regression

Regression in commit 2caa80e7
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Sun Feb 22 11:38:36 2015 +0100

    drm: Fix deadlock due to getconnector locking changes

If the drm_connector_find() call returns NULL, we should no longer
call drm_modeset_unlock() to avoid locking imbalance.
Signed-off-by: Tommi Rantala <tt.rantala@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_crtc.c

@@ -2121,7 +2121,7 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
 	connector = drm_connector_find(dev, out_resp->connector_id);
 	if (!connector) {
 		ret = -ENOENT;
-		goto out;
+		goto out_unlock;
 	}
 
 	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++)
@@ -2201,6 +2201,8 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
 
 out:
 	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+out_unlock:
 	mutex_unlock(&dev->mode_config.mutex);
 
 	return ret;