drm/fsl-dcu: Use drm_plane_helper_destroy()

Replace the driver's own function with drm_plane_helper_destroy(). No
functional changes.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Reviewed-by: Sam Ravnborg <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_plane.c

···
 #include <drm/drm_fourcc.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem_cma_helper.h>
+#include <drm/drm_plane_helper.h>
 #include <drm/drm_probe_helper.h>
 
 #include "fsl_dcu_drm_drv.h"
···
 	.atomic_update = fsl_dcu_drm_plane_atomic_update,
 };
 
-static void fsl_dcu_drm_plane_destroy(struct drm_plane *plane)
-{
-	drm_plane_cleanup(plane);
-	kfree(plane);
-}
-
 static const struct drm_plane_funcs fsl_dcu_drm_plane_funcs = {
 	.atomic_duplicate_state = drm_atomic_helper_plane_duplicate_state,
 	.atomic_destroy_state = drm_atomic_helper_plane_destroy_state,
-	.destroy = fsl_dcu_drm_plane_destroy,
+	.destroy = drm_plane_helper_destroy,
 	.disable_plane = drm_atomic_helper_disable_plane,
 	.reset = drm_atomic_helper_plane_reset,
 	.update_plane = drm_atomic_helper_update_plane,