xps: Add xps_queue_release function

This patch moves the xps specific parts in netdev_queue_release into
its own function which netdev_queue_release can call.  This allows
netdev_queue_release to be more generic (for adding new attributes
to tx queues).

Signed-off-by: Tom Herbert <therbert@google.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>