drm/ttm: Ignore signaled move fences

Move fences that have already signaled should not prevent memory
allocations with no_wait_gpu.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210227034524.21763-1-Felix.Kuehling@amd.comSigned-off-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/ttm/ttm_bo.c

@@ -705,8 +705,9 @@ static int ttm_bo_add_move_fence(struct ttm_buffer_object *bo,
 		return 0;
 
 	if (no_wait_gpu) {
+		ret = dma_fence_is_signaled(fence) ? 0 : -EBUSY;
 		dma_fence_put(fence);
-		return -EBUSY;
+		return ret;
 	}
 
 	dma_resv_add_shared_fence(bo->base.resv, fence);