mlxsw: spectrum_router: Move here inetaddr validator notifiers

The validation logic is already in the router code. Move there the notifier
blocks themselves as well.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>