ACPI / processor: Introduce invalid_phys_cpuid()

Introduce invalid_phys_cpuid() to identify cpu with invalid
physical ID, then used it as replacement of the direct comparisons
with PHYS_CPUID_INVALID.

Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
index fd4140d..33a38d6 100644
--- a/drivers/acpi/processor_core.c
+++ b/drivers/acpi/processor_core.c
@@ -184,7 +184,7 @@
 	phys_cpuid_t phys_id;
 
 	phys_id = map_mat_entry(handle, type, acpi_id);
-	if (phys_id == PHYS_CPUID_INVALID)
+	if (invalid_phys_cpuid(phys_id))
 		phys_id = map_madt_entry(type, acpi_id);
 
 	return phys_id;
@@ -196,7 +196,7 @@
 	int i;
 #endif
 
-	if (phys_id == PHYS_CPUID_INVALID) {
+	if (invalid_phys_cpuid(phys_id)) {
 		/*
 		 * On UP processor, there is no _MAT or MADT table.
 		 * So above phys_id is always set to PHYS_CPUID_INVALID.