net: dsa: b53: prevent standalone from trying to forward to other ports

net: dsa: b53: prevent standalone from trying to forward to other ports

When bridged ports and standalone ports share a VLAN, e.g. via VLAN
uppers, or untagged traffic with a vlan unaware bridge, the ASIC will
still try to forward traffic to known FDB entries on standalone ports.
But since the port VLAN masks prevent forwarding to bridged ports, this
traffic will be dropped.

This e.g. can be observed in the bridge_vlan_unaware ping tests, where
this breaks pinging with learning on.

Work around this by enabling the simplified EAP mode on switches
supporting it for standalone ports, which causes the ASIC to redirect
traffic of unknown source MAC addresses to the CPU port.

Since standalone ports do not learn, there are no known source MAC
addresses, so effectively this redirects all incoming traffic to the CPU
port.

Fixes: ff39c2d68679 ("net: dsa: b53: Add bridge support")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://patch.msgid.link/20250508091424.26870-1-jonas.gorski@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>