wil6210: use kfree_skb() instead of kfree()

Use kfree_skb() instead of kfree() to free sk_buff.

Introduced by commit e270045b
(wil6210: Sanity check for reported DMA length)
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/wil6210/txrx.c

@@ -369,7 +369,7 @@ static struct sk_buff *wil_vring_reap_rx(struct wil6210_priv *wil,
 
 	if (dmalen > sz) {
 		wil_err(wil, "Rx size too large: %d bytes!\n", dmalen);
-		kfree(skb);
+		kfree_skb(skb);
 		return NULL;
 	}
 	skb_trim(skb, dmalen);