mlxsw: spectrum_router: mlxsw_sp_inetaddr_bridge_event: Add an argument

For purposes of replay, mlxsw_sp_inetaddr_bridge_event() will need to make
decisions based on the proposed value of PVID. Querying PVID reveals the
current settings, not the in-flight values that the user requested and that
the notifiers are acting upon. Add a parameter, lower_pvid, which carries
the proposed PVID of the lower bridge, or -1 if the lower is not a bridge.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Danielle Ratson <danieller@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>