mlxsw: spectrum_router: Take router lock from inetaddr listeners

Another entry point into the routing code is from inetaddr listeners.
The driver registers listeners to IPv4 and IPv6 inetaddr notification
chains in order to understand when a RIF needs to be created or
destroyed.

Serialize access to shared router structures from these listeners by
taking the router lock when processing inetaddr events.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>