drm/amdgpu: add reference for **fence

fix fence is released when pass to **fence sometimes.
add reference for it.

Signed-off-by: Chunming Zhou <david1.zhou@amd.com>
Reviewed-by: Christian K?nig <christian.koenig@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c
index 38660ea..33ee6ae 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c
@@ -415,6 +415,7 @@
 		goto err;
 	if (fence)
 		*fence = fence_get(f);
+	fence_put(f);
 	if (amdgpu_enable_scheduler)
 		return 0;
 err:
@@ -481,6 +482,7 @@
 		goto err;
 	if (fence)
 		*fence = fence_get(f);
+	fence_put(f);
 	if (amdgpu_enable_scheduler)
 		return 0;
 err: