Repurpose a currently unused macro to make it usable for common SFP port
definitions. Do so by changing defined properties, drop the fixed link,
etc.
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/22827
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>