net: stmmac: fix errno when create_singlethread_workqueue() fails

We should set the return value to -ENOMEM explicitly when
create_singlethread_workqueue() fails in stmmac_dvr_probe(),
otherwise we'll lose the error value.

Fixes: a137f3f ("net: stmmac: fix possible memory leak in stmmac_dvr_probe()")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/20221214080117.3514615-1-cuigaosheng1@huawei.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -7099,6 +7099,7 @@ int stmmac_dvr_probe(struct device *device,
 	priv->wq = create_singlethread_workqueue("stmmac_wq");
 	if (!priv->wq) {
 		dev_err(priv->device, "failed to create workqueue\n");
+		ret = -ENOMEM;
 		goto error_wq_init;
 	}