cpuidle: Single/Global registration of idle states

This patch makes the cpuidle_states structure global (single copy)
instead of per-cpu. The statistics needed on per-cpu basis
by the governor are kept per-cpu. This simplifies the cpuidle
subsystem as state registration is done by single cpu only.
Having single copy of cpuidle_states saves memory. Rare case
of asymmetric C-states can be handled within the cpuidle driver
and architectures such as POWER do not have asymmetric C-states.

Having single/global registration of all the idle states,
dynamic C-state transitions on x86 are handled by
the boot cpu. Here, the boot cpu  would disable all the devices,
re-populate the states and later enable all the devices,
irrespective of the cpu that would receive the notification first.

Reference:
https://lkml.org/lkml/2011/4/25/83

Signed-off-by: Deepthi Dharwar <[email protected]>
Signed-off-by: Trinabh Gupta <[email protected]>
Tested-by: Jean Pihet <[email protected]>
Reviewed-by: Kevin Hilman <[email protected]>
Acked-by: Arjan van de Ven <[email protected]>
Acked-by: Kevin Hilman <[email protected]>
Signed-off-by: Len Brown <[email protected]>

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