drm/amdgpu: fix leaking fence in the pageflip code

This fixes a memory leak when we can't register the callback on a fence.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_display.c

@@ -57,7 +57,7 @@ static bool amdgpu_flip_handle_fence(struct amdgpu_flip_work *work,
 	if (!fence_add_callback(fence, &work->cb, amdgpu_flip_callback))
 		return true;
 
-	fence_put(*f);
+	fence_put(fence);
 	return false;
 }