cpuidle: replace xen access to x86 pm_idle and default_idle

cpuidle: replace xen access to x86 pm_idle and default_idle

When a Xen Dom0 kernel boots on a hypervisor, it gets access
to the raw-hardware ACPI tables.  While it parses the idle tables
for the hypervisor's beneift, it uses HLT for its own idle.

Rather than have xen scribble on pm_idle and access default_idle,
have it simply disable_cpuidle() so acpi_idle will not load and
architecture default HLT will be used.

cc: [email protected]
Tested-by: Konrad Rzeszutek Wilk <[email protected]>
Acked-by: H. Peter Anvin <[email protected]>
Signed-off-by: Len Brown <[email protected]>