netvsc: fix error unwind on device setup failure

If setting receive buffer fails, the error unwind would cause
kernel panic because it was not correctly doing RCU and NAPI
unwind.  RCU'd pointer needs to be reset to NULL, and NAPI needs
to be disabled not deleted.
Signed-off-by: NStephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/hyperv/netvsc.c

@@ -1307,7 +1307,8 @@ struct netvsc_device *netvsc_device_add(struct hv_device *device,
 	return net_device;
 
 close:
-	netif_napi_del(&net_device->chan_table[0].napi);
+	RCU_INIT_POINTER(net_device_ctx->nvdev, NULL);
+	napi_disable(&net_device->chan_table[0].napi);
 
 	/* Now, we can close the channel safely */
 	vmbus_close(device->channel);