arm64: ipi_nmi: fix compile error when CONFIG_KGDB is disabled

hulk inclusion
category: bugfix
bugzilla: 50485
CVE: NA

-------------------------------------------------------------------------

Fix the following compile error.

arch/arm64/kernel/ipi_nmi.c: In function ‘ipi_nmi_handler’:
arch/arm64/kernel/ipi_nmi.c:54:7: error: implicit declaration of function ‘kgdb_nmicallback’ [-Werror=implicit-function-declaration]
  if (!kgdb_nmicallback(cpu, get_irq_regs()))
       ^~~~~~~~~~~~~~~~
Signed-off-by: NXiongfeng Wang <wangxiongfeng2@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/arm64/kernel/ipi_nmi.c

@@ -46,13 +46,14 @@ bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 static irqreturn_t ipi_nmi_handler(int irq, void *data)
 {
 	irqreturn_t ret = IRQ_NONE;
-	unsigned int cpu = smp_processor_id();
 
 	if (nmi_cpu_backtrace(get_irq_regs()))
 		ret = IRQ_HANDLED;
 
-	if (!kgdb_nmicallback(cpu, get_irq_regs()))
+#ifdef CONFIG_KGDB
+	if (!kgdb_nmicallback(smp_processor_id(), get_irq_regs()))
 		ret = IRQ_HANDLED;
+#endif
 
 	return ret;
 }