drm/nouveau: use drm_gem_plane_helper_prepare_fb

Instead of manually adjusting the plane state.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220429134230.24334-3-christian.koenig@amd.com

drivers/gpu/drm/nouveau/dispnv50/wndw.c

@@ -32,6 +32,7 @@
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_gem_atomic_helper.h>
 #include <drm/drm_fourcc.h>
 
 #include "nouveau_bo.h"
@@ -558,9 +559,7 @@ nv50_wndw_prepare_fb(struct drm_plane *plane, struct drm_plane_state *state)
 			asyw->image.handle[0] = ctxdma->object.handle;
 	}
 
-	ret = dma_resv_get_singleton(nvbo->bo.base.resv,
-				     DMA_RESV_USAGE_WRITE,
-				     &asyw->state.fence);
+	ret = drm_gem_plane_helper_prepare_fb(plane, state);
 	if (ret)
 		return ret;