net: ethernet: mtk_eth_soc: fix error code in mtk_flow_offload_replace()

Preserve the error code from mtk_foe_entry_commit().  Do not return
success.

Fixes: c4f033d9 ("net: ethernet: mtk_eth_soc: rework hardware flow table management")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>