arch: x86: Use ACPICA typdef instead of struct name

Use ACPI_MADT_LOCAL_APIC instead of struct acpi_madt_local_apic. In the
same go, switch to IF_ENABLED from ifdef - slightly more readable, and
this keeps some static analyzers happy (e.g. upstream Compliance check).

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
diff --git a/arch/x86/core/intel64/cpu.c b/arch/x86/core/intel64/cpu.c
index 6afcec2..a522e87 100644
--- a/arch/x86/core/intel64/cpu.c
+++ b/arch/x86/core/intel64/cpu.c
@@ -144,14 +144,14 @@
 	uint8_t vector = ((unsigned long) x86_ap_start) >> 12;
 	uint8_t apic_id;
 
-#ifdef CONFIG_ACPI
-	struct acpi_madt_local_apic *lapic = acpi_local_apic_get(cpu_num);
+	IF_ENABLED(CONFIG_ACPI, ({
+		ACPI_MADT_LOCAL_APIC *lapic = acpi_local_apic_get(cpu_num);
 
-	if (lapic != NULL) {
-		/* We update the apic_id, __start will need it. */
-		x86_cpu_loapics[cpu_num] = lapic->Id;
-	}
-#endif
+		if (lapic != NULL) {
+			/* We update the apic_id, __start will need it. */
+			x86_cpu_loapics[cpu_num] = lapic->Id;
+		}
+	}));
 
 	apic_id = x86_cpu_loapics[cpu_num];