When BRIDGE is a loadable module, MLXSW_SPECTRUM mustn't be built-in:

drivers/built-in.o: In function `mlxsw_sp_bridge_device_create':
drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c:145: undefined reference to `br_vlan_enabled'
drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c:158: undefined reference to `br_multicast_enabled'
drivers/built-in.o: In function `mlxsw_sp_dev_rif_type':
drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:2972: undefined reference to `br_vlan_enabled'
drivers/built-in.o: In function `mlxsw_sp_inetaddr_vlan_event':
drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:3310: undefined reference to `br_vlan_enabled'

Add Kconfig dependency to enforce usable configurations.

Fixes: c57529e1 ("mlxsw: spectrum: Replace vPorts with Port-VLAN")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reported-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Tested-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>