Set error value when allocation of IO irq fails in ENA

bus_alloc_resource_any() is not returning error value in case of an
error.
If the function call fails, the error value was not passed to the
ena_up() function.

Submitted by:  Michal Krawczyk <mk@semihalf.com>
Obtained from: Semihalf
Sponsored by:  Amazon, Inc.

sys/dev/ena/ena.c

@@ -1998,6 +1998,7 @@ ena_request_io_irq(struct ena_adapter *adapter)
 		irq->res = bus_alloc_resource_any(adapter->pdev, SYS_RES_IRQ,
 		    &irq->vector, flags);
 		if (unlikely(irq->res == NULL)) {
+			rc = ENOMEM;
 			device_printf(adapter->pdev, "could not allocate "
 			    "irq vector: %d\n", irq->vector);
 			goto err;