ACPI: C-States: accounting of sleep states

Track the actual time spent in C-States (C2 upwards, we can't determine this
for C1), not only the number of invocations.  This is especially useful for
dynamic ticks / "tickless systems", but is also of interest on normal systems,
as any interrupt activity leads to C-States being exited, not only the timer
interrupt.

The time is being measured in PM timer ticks, so an increase by one equals 279
nanoseconds.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>

include/acpi/processor.h

@@ -62,6 +62,7 @@ struct acpi_processor_cx {
 	u32 latency_ticks;
 	u32 power;
 	u32 usage;
+	u64 time;
 	struct acpi_processor_cx_policy promotion;
 	struct acpi_processor_cx_policy demotion;
 };