net: bridge: rename fdb_insert to fdb_add_local

fdb_insert() is not a descriptive name for this function, and also easy
to confuse with __br_fdb_add(), fdb_add_entry(), br_fdb_update().
Even more confusingly, it is not even related in any way with those
functions, neither one calls the other.

Since fdb_insert() basically deals with the creation of a BR_FDB_LOCAL
entry and is called only from functions where that is the intention:

- br_fdb_changeaddr
- br_fdb_change_mac_address
- br_fdb_insert

then rename it to fdb_add_local(), because its removal counterpart is
called fdb_delete_local().

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>