net: enable memcg accounting for veth queues

veth netdevice defines own rx queues and allocates array containing
up to 4095 ~750-bytes-long 'struct veth_rq' elements. Such allocation
is quite huge and should be accounted to memcg.

Signed-off-by: Vasily Averin <vvs@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>