rtw88: fix use after free in rtw_hw_scan_update_probe_req()

This code needs to use skb_queue_walk_safe() instead of skb_queue_walk()
because it frees the list iterator.

Fixes: d95984b5 ("rtw88: fix memory overrun and memory leak during hw_scan")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220203082532.GA25151@kili