realtek: d-link dgs-1210-10p improve sfp support

realtek: d-link dgs-1210-10p improve sfp support

The current dts file of dgs-1210-10p doesn't support link states
for the sfp ports (they are always up).
This patch tries to give better support for this and was run tested
on dgs-1210-10p.

It was heavily inspired from Paul Fertser, RaylynnKnight
and the author of dgs-1210-10mp-f.dts

https://forum.openwrt.org/t/dlink-dgs-1210-10p-with-glc-t-co-sfp/170928

Signed-off-by: Michel Thill <jmthill@gmail.com>