net: iwlwifi: use skb_list_walk_safe helper for gso segments

This is a straight-forward conversion case for the new function, and
while we're at it, we can remove a null write to skb->next by replacing
it with skb_mark_not_on_list.
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/wireless/intel/iwlwifi/mvm/tx.c

@@ -847,10 +847,7 @@ iwl_mvm_tx_tso_segment(struct sk_buff *skb, unsigned int num_subframes,
 	else if (next)
 		consume_skb(skb);
 
-	while (next) {
-		tmp = next;
-		next = tmp->next;
-
+	skb_list_walk_safe(next, tmp, next) {
 		memcpy(tmp->cb, cb, sizeof(tmp->cb));
 		/*
 		 * Compute the length of all the data added for the A-MSDU.
@@ -880,9 +877,7 @@ iwl_mvm_tx_tso_segment(struct sk_buff *skb, unsigned int num_subframes,
 			skb_shinfo(tmp)->gso_size = 0;
 		}
 
-		tmp->prev = NULL;
-		tmp->next = NULL;
-
+		skb_mark_not_on_list(tmp);
 		__skb_queue_tail(mpdus_skb, tmp);
 		i++;
 	}