net: dsa: mv88e6xxx: Fix number of databases for 88E6141 / 88E6341

The Topaz family (88E6141 and 88E6341) only support 256 Forwarding
Information Tables.

Fixes: a75961d0 ("net: dsa: mv88e6xxx: Add support for ethernet switch 88E6341")
Fixes: 1558727a

 ("net: dsa: mv88e6xxx: Add support for ethernet switch 88E6141")
Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20240429133832.9547-1-kabel@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>