net: dsa: b53: fix learning on VLAN unaware bridges

net: dsa: b53: fix learning on VLAN unaware bridges

When VLAN filtering is off, we configure the switch to forward, but not
learn on VLAN table misses. This effectively disables learning while not
filtering.

Fix this by switching to forward and learn. Setting the learning disable
register will still control whether learning actually happens.

Fixes: dad8d7c6452b ("net: dsa: b53: Properly account for VLAN filtering")
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/20250429201710.330937-11-jonas.gorski@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>