drm: renesas: shmobile: Remove custom plane destroy callback

There is no need to call drm_plane_force_disable() from the plane's
.destroy() callback, as the plane should have been disabled already
before.  See also commit 3c858a33 ("drm/plane_helper: don't
disable plane in destroy function") for the generic plane helper case.

After removing this call, shmob_drm_plane_destroy() becomes a simple
wrapper around shmob_drm_plane_destroy(), hence replace it by the
latter.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/8d7a3f250612085fdf4e06d377843e8f874b22d9.1694767209.git.geert+renesas@glider.be

drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c

@@ -176,16 +176,10 @@ static int shmob_drm_plane_disable(struct drm_plane *plane,
 	return 0;
 }
 
-static void shmob_drm_plane_destroy(struct drm_plane *plane)
-{
-	drm_plane_force_disable(plane);
-	drm_plane_cleanup(plane);
-}
-
 static const struct drm_plane_funcs shmob_drm_plane_funcs = {
 	.update_plane = shmob_drm_plane_update,
 	.disable_plane = shmob_drm_plane_disable,
-	.destroy = shmob_drm_plane_destroy,
+	.destroy = drm_plane_cleanup,
 };
 
 static const uint32_t formats[] = {