selinux: add the "attach_queue" permission to the "tun_socket" class

Add a new permission to align with the new TUN multiqueue support,
"tun_socket:attach_queue".

The corresponding SELinux reference policy patch is show below:

 diff --git a/policy/flask/access_vectors b/policy/flask/access_vectors
 index 28802c5..a0664a1 100644
 --- a/policy/flask/access_vectors
 +++ b/policy/flask/access_vectors
 @@ -827,6 +827,9 @@ class kernel_service

  class tun_socket
  inherits socket
 +{
 +       attach_queue
 +}

  class x_pointer
  inherits x_device

Signed-off-by: Paul Moore <pmoore@redhat.com>
Acked-by: Eric Paris <eparis@parisplace.org>
Tested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>