The port media handling introduced before was to some extent just taken
over from the SDK. As a second step, improve that code now. Some code
can be deduplicated, a few statements removed and improved in general.
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21385
Signed-off-by: Robert Marko <robimarko@gmail.com>