mlxsw: spectrum_router: Only handle IPv4 and IPv6 events

The driver doesn't support events from address families other than IPv4
and IPv6, so ignore them. Otherwise, we risk queueing a work item before
it's initialized.

This can happen in case a VRF is configured when MROUTE_MULTIPLE_TABLES
is enabled, as the VRF driver will try to add an l3mdev rule for the
IPMR family.

Fixes: 65e65ec1

 ("mlxsw: spectrum_router: Don't ignore IPv6 notifications")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reported-by: Andreas Rammhold <andreas@rammhold.de>
Reported-by: Florian Klink <flokli@flokli.de>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>