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>

arch/x86/core/intel64/cpu.c

@@ -144,14 +144,14 @@ void arch_start_cpu(int cpu_num, k_thread_stack_t *stack, int sz,
  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 (lapic != NULL) {
- /* We update the apic_id, __start will need it. */
- x86_cpu_loapics[cpu_num] = lapic->Id;
- }
-#endif
+ 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;
+  }
+ }));
 
  apic_id = x86_cpu_loapics[cpu_num];