drm: Fix locking cargo-cult in encoder/plane init/cleanup

Encoders&planes can't be hotplugged, we dont need locking for this
since it's all single-threaded driver setup/teardown code. CRTCs
already don't grab locks.

While at it I noticed that plane's are missing the
drm_modeset_lock_fini() call, so add it.

Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161129094538.9650-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_plane.c

@@ -221,7 +221,8 @@ void drm_plane_cleanup(struct drm_plane *plane)
 {
 	struct drm_device *dev = plane->dev;
 
-	drm_modeset_lock_all(dev);
+	drm_modeset_lock_fini(&plane->mutex);
+
 	kfree(plane->format_types);
 	drm_mode_object_unregister(dev, &plane->base);
 
@@ -236,7 +237,6 @@ void drm_plane_cleanup(struct drm_plane *plane)
 	dev->mode_config.num_total_plane--;
 	if (plane->type == DRM_PLANE_TYPE_OVERLAY)
 		dev->mode_config.num_overlay_plane--;
-	drm_modeset_unlock_all(dev);
 
 	WARN_ON(plane->state && !plane->funcs->atomic_destroy_state);
 	if (plane->state && plane->funcs->atomic_destroy_state)