net: fix typo in skbuff.c

Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/skbuff.c

@@ -1896,7 +1896,7 @@ void *__pskb_pull_tail(struct sk_buff *skb, int delta)
 	}
 
 	/* If we need update frag list, we are in troubles.
-	 * Certainly, it possible to add an offset to skb data,
+	 * Certainly, it is possible to add an offset to skb data,
 	 * but taking into account that pulling is expected to
 	 * be very rare operation, it is worth to fight against
 	 * further bloating skb head and crucify ourselves here instead.