veth: Free queues on link delete

David Ahern reported memory leak in veth.

=======================================================================
$ cat /sys/kernel/debug/kmemleak
unreferenced object 0xffff8800354d5c00 (size 1024):
  comm "ip", pid 836, jiffies 4294722952 (age 25.904s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<(____ptrval____)>] kmemleak_alloc+0x70/0x94
    [<(____ptrval____)>] slab_post_alloc_hook+0x42/0x52
    [<(____ptrval____)>] __kmalloc+0x101/0x142
    [<(____ptrval____)>] kmalloc_array.constprop.20+0x1e/0x26 [veth]
    [<(____ptrval____)>] veth_newlink+0x147/0x3ac [veth]
    ...
unreferenced object 0xffff88002e009c00 (size 1024):
  comm "ip", pid 836, jiffies 4294722958 (age 25.898s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<(____ptrval____)>] kmemleak_alloc+0x70/0x94
    [<(____ptrval____)>] slab_post_alloc_hook+0x42/0x52
    [<(____ptrval____)>] __kmalloc+0x101/0x142
    [<(____ptrval____)>] kmalloc_array.constprop.20+0x1e/0x26 [veth]
    [<(____ptrval____)>] veth_newlink+0x219/0x3ac [veth]
=======================================================================

veth_rq allocated in veth_newlink() was not freed on dellink.

We need to free up them after veth_close() so that any packets will not
reference the queues afterwards. Thus free them in veth_dev_free() in
the same way as freeing stats structure (vstats).

Also move queues allocation to veth_dev_init() to be in line with stats
allocation.

Fixes: 638264dc ("veth: Support per queue XDP ring")
Reported-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Reviewed-by: David Ahern <dsahern@gmail.com>
Tested-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>