x86/jailhouse: Silence ACPI warning

Jailhouse support does not depend on ACPI, and does not even use it. But
if it should be enabled, avoid warning about its absence in the
platform.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: jailhouse-dev@googlegroups.com
Link: https://lkml.kernel.org/r/939687007cbd7643b02fd330e8616e7e5944063f.1511770314.git.jan.kiszka@siemens.com