lantiq: xrx200: switch the subtarget to the mainline DSA driver

lantiq: xrx200: switch the subtarget to the mainline DSA driver

Enable the XRX200 PMAC, GSWIP DSA tag and GSIP DSA drivers in the 5.4
kernel config. Update the existing vr9_*.dts{,i} to use the new
Ethernet and switch drivers. Drop the swconfig package from the xrx200
target because swconfig doesn't manage DSA based switches.

The new /etc/config/network format for the DSA driver is not compatible
with the old (swconfig) based one. Show a message during sysupgrade
notifying users about this change and asking them to start with a fresh
config (or forcefully update and then migrate the config manually).

Failsafe mode can now automatically bring up the first lan interface
based on board.json including DSA based setups. Drop
05_set_preinit_iface_lantiq from the xRX200 sub-target as this is not
needed anymore. For now we are keeping it for the ase, xway and
xway_legacy until there's some confirmation that it can be dropped from
there as well.

While here, some boards also receive minor fixups:
- Use LAN1 as LAN1 (according to a photo this port can also be
  configured as WAN) on the Buffalo WBMR-300HPD. This makes it easier to
  read the port mapping because otherwise we would have LAN{2,3,4} and
  WAN (which was the case for the non-DSA version previously).
- vr9_avm_fritz3390.dts: move the "gpio" comment from port 0 and 1 to
  their corresponding PHYs
- vr9_tplink_vr200.dtsi: move the "gpio" comment from port 0 to PHY 0
- vr9_tplink_tdw89x0.dtsi: move the "gpio" comment from port 0 to PHY 0

Acked-by: Aleksander Jan Bajkowski <A.Bajkowski@stud.elka.pw.edu.pl>
Tested-by: Notupus <notpp46@googlemail.com> # TD-W9980/DM200/FRITZ 7430
Tested-by: Martin Schiller <ms@dev.tdt.de> # tested on TDT VR2020
Tested-by: Martin Schiller <ms@dev.tdt.de> # tested on TP-Link TD-W8980B
Tested-by: Martin Schiller <ms@dev.tdt.de> # tested on ZyXEL P-2812HNU-F1
Tested-by: Daniel Kestrel <kestrel1974@t-online.de> # tested on Fritzbox 7490
Tested-by: Daniel Kestrel <kestrel1974@t-online.de> # tested on Fritzbox 3490
Tested-by: @jospezial <jospezial@gmx.de> # tested on VGV7510KW22 (o2 Box 6431)
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>