iwmc3200wifi: replace netif_rx with netif_rx_ni

The patch uses netif_rx_ni() over netif_rx() to post buffers to
upper network code because it is always scheduled in a workqueue.
The problem was first observed from a dynamic ticks warning:

    "NOHZ: local_softirq_pending ..."
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwmc3200wifi/rx.c

@@ -1373,7 +1373,7 @@ static void iwm_rx_process_packet(struct iwm_priv *iwm,
 		ndev->stats.rx_packets++;
 		ndev->stats.rx_bytes += skb->len;
 
-		if (netif_rx(skb) == NET_RX_DROP) {
+		if (netif_rx_ni(skb) == NET_RX_DROP) {
 			IWM_ERR(iwm, "Packet dropped\n");
 			ndev->stats.rx_dropped++;
 		}