drm/msm: dpu: Fix memory leak caused by dropped reference

We are currently leaking a drm_crtc_commit struct for every atomic
commit containing plane state. The dpu plane destroy function cleans up
the fb reference manually, but fails to release the commit ref. As a
result, we just keep allocating drm_crtc_commits without ever freeing
them. Fortunately there's a helper function which will clean up all of
our mess at once, so use that.

Thanks to Doug Anderson for reporting the memory leak (and leaving
breadcrumbs from kmemleak!).
Reported-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c

@@ -1203,9 +1203,7 @@ static void dpu_plane_destroy_state(struct drm_plane *plane,
 
 	pstate = to_dpu_plane_state(state);
 
-	/* remove ref count for frame buffers */
-	if (state->fb)
-		drm_framebuffer_put(state->fb);
+	__drm_atomic_helper_plane_destroy_state(state);
 
 	kfree(pstate);
 }