x86/jailhouse: Enable PMTIMER

Jailhouse exposes the PMTIMER as only reference clock to all cells. Pick
up its address from the setup data. Allow to enable the Linux support of
it by relaxing its strict dependency on ACPI.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: jailhouse-dev@googlegroups.com
Link: https://lkml.kernel.org/r/6d5c3fadd801eb3fba9510e2d3db14a9c404a1a0.1511770314.git.jan.kiszka@siemens.com