[][kernel][common][eth][Introduce device register map]

[Description]
Add device register map.

This modification refers to Linux upstream patch which came from
Lorenzo Bianconi.
  - v3-net-next-12-16-net-ethernet-mtk_eth_soc-introduce-device-
  register-map.diff

[Release-log]
N/A


Change-Id: I92fb1a224ebef75571b2dc29909b87514eba3a2b
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7001134
2 files changed