Simplify pcifront's shared page creation and removal via
xenbus_setup_ring() and xenbus_teardown_ring().
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>