x86/acpi: use FADT flags to determine the PMTMR width

x86/acpi: use FADT flags to determine the PMTMR width

On some computers the bit width of the PM Timer as reported
by ACPI is 32 bits when in fact the FADT flags report correctly
that the timer is 24 bits wide. On affected machines such as the
ASUS FX504GM and never gaming laptops this results in the inability
to resume the machine from suspend. Without this patch suspend is
broken on affected machines and even if a machine manages to resume
correctly then the kernel time and xen timers are trashed.

Signed-off-by: Grzegorz Uriasz <gorbak25@gmail.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Paul Durrant <paul@xen.org>