[][Add hw path for 2.5G LAN <-> 2.5G WAN]

[Description]
Add hw path support for
2.5G LAN (mt7531 port 5) <-> 2.5G WAN (GMAC2).

[Release-log]
N/A

Change-Id: I64426c0554c1096134114febde0e8cb8ac4bca7a
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/4562385
3 files changed