Network interface groups support added while ago, however
there is no IFLA_GROUP attribute description in policy
and netlink message size calculations until now.
Add IFLA_GROUP attribute to the policy.
Fixes: cbda10fa97d7 ("net_device: add support for network device groups") Signed-off-by: Serhey Popovych <serhe.popovych@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>