devinet: fix memleak in inetdev_init()

When devinet_sysctl_register() failed, the memory allocated
in neigh_parms_alloc() should be freed.

Fixes: 20e61da7

 ("ipv4: fail early when creating netdev named all or default")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>