net: ena: Fix error handling in ena_init()

The ena_init() won't destroy workqueue created by
create_singlethread_workqueue() when pci_register_driver() failed.
Call destroy_workqueue() when pci_register_driver() failed to prevent the
resource leak.

Fixes: 1738cd3e ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Yuan Can <yuancan@huawei.com>
Acked-by: Shay Agroskin <shayagr@amazon.com>
Link: https://lore.kernel.org/r/20221114025659.124726-1-yuancan@huawei.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/amazon/ena/ena_netdev.c

@@ -4543,13 +4543,19 @@ static struct pci_driver ena_pci_driver = {
 
 static int __init ena_init(void)
 {
+	int ret;
+
 	ena_wq = create_singlethread_workqueue(DRV_MODULE_NAME);
 	if (!ena_wq) {
 		pr_err("Failed to create workqueue\n");
 		return -ENOMEM;
 	}
 
-	return pci_register_driver(&ena_pci_driver);
+	ret = pci_register_driver(&ena_pci_driver);
+	if (ret)
+		destroy_workqueue(ena_wq);
+
+	return ret;
 }
 
 static void __exit ena_cleanup(void)