Add error handling to the ENA driver if init of the reset task fails

Also, to simplify cleaning routine, reset task is initialized before
allocating statistics and other resources.

Submitted by:   Michal Krawczyk <mk@semihalf.com>
Obtained from:  Semihalf
Sponsored by:   Amazon.com Inc.
Differential revision: https://reviews.freebsd.org/D10925

sys/dev/ena/ena.c

@@ -3604,6 +3604,18 @@ ena_attach(device_t pdev)
 		goto err_ifp_free;
 	}
 
+	/* Initialize reset task queue */
+	TASK_INIT(&adapter->reset_task, 0, ena_reset_task, adapter);
+	adapter->reset_tq = taskqueue_create("ena_reset_enqueue",
+	    M_WAITOK | M_ZERO, taskqueue_thread_enqueue, &adapter->reset_tq);
+	if (adapter->reset_tq == NULL) {
+		device_printf(adapter->pdev,
+		    "Unable to create reset task queue\n");
+		goto err_reset_tq;
+	}
+	taskqueue_start_threads(&adapter->reset_tq, 1, PI_NET,
+	    "%s rstq", device_get_nameunit(adapter->pdev));
+
 	/* Initialize statistics */
 	ena_alloc_counters((counter_u64_t *)&adapter->dev_stats,
 	    sizeof(struct ena_stats_dev));
@@ -3613,16 +3625,12 @@ ena_attach(device_t pdev)
 	/* Tell the stack that the interface is not active */
 	if_setdrvflagbits(adapter->ifp, IFF_DRV_OACTIVE, IFF_DRV_RUNNING);
 
-	/* Initialize reset task queue */
-	TASK_INIT(&adapter->reset_task, 0, ena_reset_task, adapter);
-	adapter->reset_tq = taskqueue_create("ena_reset_enqueue",
-	    M_WAITOK | M_ZERO, taskqueue_thread_enqueue, &adapter->reset_tq);
-	taskqueue_start_threads(&adapter->reset_tq, 1, PI_NET,
-	    "%s rstq", device_get_nameunit(adapter->pdev));
-
 	adapter->running = true;
 	return (0);
 
+err_reset_tq:
+	ena_free_mgmnt_irq(adapter);
+	ena_disable_msix(adapter);
 err_ifp_free:
 	if_detach(adapter->ifp);
 	if_free(adapter->ifp);