staging: rtl8188eu: use safe iterator in rtw_free_network_queue

staging: rtl8188eu: use safe iterator in rtw_free_network_queue

rtw_free_network_queue iterates over the scanned wireless networks and
calls _rtw_free_network for each of them. In some cases,
_rtw_free_network removes a network from the list.

We have to use list_for_each_entry_safe if we remove list entries while
we iterate over a list.

Fixes: 23017c8842d2 ("staging: rtl8188eu: Use list iterators and helpers")
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210517201826.25150-1-martin@kaiser.cx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>