net: dsa: b53: do not allow to configure VLAN 0

Since we cannot set forwarding destinations per VLAN, we should not have
a VLAN 0 configured, as it would allow untagged traffic to work across
ports on VLAN aware bridges regardless if a PVID untagged VLAN exists.

So remove the VLAN 0 on join, an re-add it on leave. But only do so if
we have a VLAN aware bridge, as without it, untagged traffic would
become tagged with VID 0 on a VLAN unaware bridge.

Fixes: a2482d2c ("net: dsa: b53: Plug in VLAN support")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20250429201710.330937-8-jonas.gorski@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>