net: prevent a NULL deref in rtnl_create_link()

In the Linux kernel, the following vulnerability has been resolved:

net: prevent a NULL deref in rtnl_create_link()

At the time rtnl_create_link() is running, dev->netdev_ops is NULL,
we must not use netdev_lock_ops() or risk a NULL deref if
CONFIG_NET_SHAPER is defined.

Use netif_set_group() instead of dev_set_group().

RIP: 0010:netdev_need_ops_lock include/net/netdev_lock.h:33 [inline]
RIP: 0010:netdev_lock_ops include/net/netdev_lock.h:41 [inline]
RIP: 0010:dev_set_group+0xc0/0x230 net/core/dev_api.c:82
Call Trace:
<TASK>
rtnl_create_link+0x748/0xd10 net/core/rtnetlink.c:3674
rtnl_newlink_create+0x25c/0xb00 net/core/rtnetlink.c:3813
__rtnl_newlink net/core/rtnetlink.c:3940 [inline]
rtnl_newlink+0x16d6/0x1c70 net/core/rtnetlink.c:4055
rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6944
netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2534
netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339
netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
sock_sendmsg_nosec net/socket.c:712 [inline]