x86 ACPI: Add support for Always Running APIC timer

Add support for Always Running APIC timer, CPUID_0x6_EAX_Bit2.
This bit means the APIC timer continues to run even when CPU is
in deep C-states.

The advantage is that we can use LAPIC timer on these CPUs
always, and there is no need for "slow to read and program"
external timers (HPET/PIT) and the timer broadcast logic
and related code in C-state entry and exit.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Len Brown <len.brown@intel.com>

arch/x86/kernel/cpu/addon_cpuid_features.c

@@ -31,6 +31,7 @@ void __cpuinit init_scattered_cpuid_features(struct cpuinfo_x86 *c)
 
 	static const struct cpuid_bit __cpuinitconst cpuid_bits[] = {
 		{ X86_FEATURE_IDA, CR_EAX, 1, 0x00000006 },
+		{ X86_FEATURE_ARAT, CR_EAX, 2, 0x00000006 },
 		{ 0, 0, 0, 0 }
 	};