[][kernel][common][eth][Add 1000basex support and refactor to upstream style for the SGMII]

[Description]
Add 1000basex support and refactor to upstream style for the SGMII.

Current support types:
    - 1000BASEX w/wo autoneg
    - SGMII w autoneg
    - HSGMII wo autoneg

If without this patch, the SGMII might unable to link with the 1000basex
link partner.

[Release-log]
N/A


Change-Id: I457b84ee944c259b7fe1c61936bb7d2b431cfee2
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7378663
4 files changed