realtek: pcs: revive dead ports after RTL8382M start

realtek: pcs: revive dead ports after RTL8382M start

SerDes attached ports that are connected during switch
boot might not be able to transmit any data after SerDes
setup. Especially ports that passed traffic before (e.g.
for tftp initramfs boot) seem to be affected. Ports that
are connected later do not show this issue.

It turns out that the old SerDes setup never really worked
on RTL8382 and the pcs refactoring (with dynamic SerDes
start and stop) totally changed the order of network bringup
in contrast to Realtek SDK.

Fix this by restaring the switch queue whenever a SerDes
goes up for the first time.

Fixes: e956adf ("realtek: rtl838x: setup SDS in PCS driver")
Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/21956
Signed-off-by: Robert Marko <robimarko@gmail.com>