net: dsa: b53: allow leaky reserved multicast

Allow reserved multicast to ignore VLAN membership so STP and other
management protocols work without a PVID VLAN configured when using a
vlan aware bridge.

Fixes: 967dd82f ("net: dsa: b53: Add support for Broadcom RoboSwitch")
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/20250429201710.330937-2-jonas.gorski@gmail.com


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