vm-virtio: Define a separate macro alias for ctrl queue devices

Now that we have factorized the common virtio pausable implementation,
it's cleaner to have a dedicated macro for control queue devices rather
than overload the macro prototype.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

vm-virtio/src/vhost_user/net.rs

@@ -361,6 +361,6 @@ impl VirtioDevice for Net {
     }
 }
 
-virtio_pausable!(Net, true);
+virtio_ctrl_q_pausable!(Net);
 impl Snapshotable for Net {}
 impl Migratable for Net {}