net: skbuff: disambiguate argument and member for skb_list_walk_safe helper

This worked before, because we made all callers name their next pointer
"next". But in trying to be more "drop-in" ready, the silliness here is
revealed. This commit fixes the problem by making the macro argument and
the member use different names.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -1479,9 +1479,9 @@ static inline void skb_mark_not_on_list(struct sk_buff *skb)
 }
 
 /* Iterate through singly-linked GSO fragments of an skb. */
-#define skb_list_walk_safe(first, skb, next)                                   \
-	for ((skb) = (first), (next) = (skb) ? (skb)->next : NULL; (skb);      \
-	     (skb) = (next), (next) = (skb) ? (skb)->next : NULL)
+#define skb_list_walk_safe(first, skb, next_skb)                               \
+	for ((skb) = (first), (next_skb) = (skb) ? (skb)->next : NULL; (skb);  \
+	     (skb) = (next_skb), (next_skb) = (skb) ? (skb)->next : NULL)
 
 static inline void skb_list_del_init(struct sk_buff *skb)
 {