net: ethernet: mtk_eth_soc: use after free in __mtk_ppe_check_skb()

The __mtk_foe_entry_clear() function frees "entry" so we have to use
the _safe() version of hlist_for_each_entry() to prevent a use after
free.

Fixes: 33fc42de

 ("net: ethernet: mtk_eth_soc: support creating mac address based offload entries")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>