ACPI: processor: introduce arch_has_acpi_pdc

arch dependent helper function that tells us if we should attempt to
evaluate _PDC on this machine or not.

The x86 implementation assumes that the CPUs in the machine must be
homogeneous, and that you cannot mix CPUs of different vendors.

Cc: Tony Luck <tony.luck@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/arch/ia64/include/asm/acpi.h b/arch/ia64/include/asm/acpi.h
index 91df968..3b788829 100644
--- a/arch/ia64/include/asm/acpi.h
+++ b/arch/ia64/include/asm/acpi.h
@@ -132,6 +132,8 @@
 extern int __initdata nid_to_pxm_map[MAX_NUMNODES];
 #endif
 
+static inline bool arch_has_acpi_pdc(void) { return true; }
+
 #define acpi_unlazy_tlb(x)
 
 #ifdef CONFIG_ACPI_NUMA