drm/writeback: remove pointless enable_signaling implementation

Just returning true here is a no-op, remove the optional callback.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20240911085903.1496-4-christian.koenig@amd.com

drivers/gpu/drm/drm_writeback.c

@@ -100,15 +100,9 @@ drm_writeback_fence_get_timeline_name(struct dma_fence *fence)
 	return wb_connector->timeline_name;
 }
 
-static bool drm_writeback_fence_enable_signaling(struct dma_fence *fence)
-{
-	return true;
-}
-
 static const struct dma_fence_ops drm_writeback_fence_ops = {
 	.get_driver_name = drm_writeback_fence_get_driver_name,
 	.get_timeline_name = drm_writeback_fence_get_timeline_name,
-	.enable_signaling = drm_writeback_fence_enable_signaling,
 };
 
 static int create_writeback_properties(struct drm_device *dev)