net: bridge: Introduce UAPI for BR_BOOLOPT_FDB_LOCAL_VLAN_0

net: bridge: Introduce UAPI for BR_BOOLOPT_FDB_LOCAL_VLAN_0

The previous patches introduced a new option, BR_BOOLOPT_FDB_LOCAL_VLAN_0.
When enabled, it has local FDB entries installed only on VLAN 0, instead of
duplicating them across all VLANs.

In this patch, add the corresponding UAPI toggle, and the code for turning
the feature on and off.

Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/ea99bfb10f687fa58091e6e1c2f8acc33f47ca45.1757004393.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>