x86/xen: fix arbitrary_virt_to_machine() While I realize that the function isn't currently being used, I still think an obvious mistake like this should be corrected. Signed-off-by: Jan Beulich <[email protected]> Acked-by: Jeremy Fitzhardinge <[email protected]> Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]>