net: skbuff.h: remove unnecessary unlikely()

WARN_ON() already contains an unlikely(), so it's not necessary to use
unlikely.

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -2508,10 +2508,8 @@ int ___pskb_trim(struct sk_buff *skb, unsigned int len);
 
 static inline void __skb_set_length(struct sk_buff *skb, unsigned int len)
 {
-	if (unlikely(skb_is_nonlinear(skb))) {
-		WARN_ON(1);
+	if (WARN_ON(skb_is_nonlinear(skb)))
 		return;
-	}
 	skb->len = len;
 	skb_set_tail_pointer(skb, len);
 }