net: dsa: b53: fix unicast/multicast flooding on BCM5325

BCM5325 doesn't implement UC_FLOOD_MASK, MC_FLOOD_MASK and IPMC_FLOOD_MASK
registers.
This has to be handled differently with other pages and registers.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20250614080000.1884236-13-noltari@gmail.com


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