net: ethernet: mtk_eth_soc: remove unneeded semicolon

Eliminate the following coccicheck warning:
 drivers/net/ethernet/mediatek/mtk_ppe.c:270:2-3: Unneeded semicolon

Signed-off-by: Qiheng Lin <linqiheng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>