[][Add non-DSA MT7531 driver support on Panther]

[Description]
Add non-DSA MT7531 driver support on Panther for 2.5G LAN/WAN
peak throughput test without additional 4-bytes special tag
used by DSA switch driver.

Driver difference:
DSA: "lan0" to "lan5" network interface for each switch port.
Non-DSA: "eth0" for all LAN ports, "eth1" for WAN port.

[Release-log]
N/A

Change-Id: I27a3efd10d1bc1709a4123331266adbf04b2ca7f
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/5422351
5 files changed