[][kernel][mt7981][eth][Add DTS for the SFP]

[Description]
Add DTS for the SFP.

Without this patch, the ETH driver is unable to bring up the SFP
modules.

[Release-log]
N/A


Change-Id: Icfa56dd09e5c5642022d985186de8f44b639b15c
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/8861262
2 files changed