Set ib1 state to MTK_FOE_STATE_UNBIND in __mtk_foe_entry_clear routine.

Fixes: 33fc42de ("net: ethernet: mtk_eth_soc: support creating mac address based offload entries")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>