net: mtk_eth: simplify the mediatek code return expression

Simplify the return expression at mtk_eth_path.c file, simplify this all.

Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Link: https://lore.kernel.org/r/20201211083801.1632-1-zhengyongjun3@huawei.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>