irqchip/riscv-aplic: Register syscore operations only once

Since commit 95a8ddd ("irqchip/riscv-aplic: Preserve APLIC
states across suspend/resume"), when multiple NUMA nodes exist
and AIA is not configured as "none", aplic_probe() is called
multiple times. This leads to register_syscore(&aplic_syscore)
being invoked repeatedly, causing the following Oops:

 list_add double add: new=ffffffffb91461f0, prev=ffffffffb91461f0, next=ffffffffb915c408.
 [<ffffffffb7b5c8ca>] __list_add_valid_or_report+0x60/0xc0
 [<ffffffffb7cc3236>] register_syscore+0x3e/0x70
 [<ffffffffb7b8d61c>] aplic_probe+0xc6/0x112

Fix this by registering syscore operations only once, using a static
variable aplic_syscore_registered to track registration.

[ tglx: Trim backtrace properly ]

Fixes: 95a8ddd ("irqchip/riscv-aplic: Preserve APLIC states across suspend/resume")
Signed-off-by: Jessica Liu <liu.xuemei1@zte.com.cn>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260310141731145xMwLsyvXl9Gw-m6A4VRYj@zte.com.cn

Author: Jessica Liu

drivers/irqchip/irq-riscv-aplic-main.c

@@ -116,6 +116,16 @@ static struct syscore aplic_syscore = {
 	.ops = &aplic_syscore_ops,
 };
 
+static bool aplic_syscore_registered __ro_after_init;
+
+static void aplic_syscore_init(void)
+{
+	if (!aplic_syscore_registered) {
+		register_syscore(&aplic_syscore);
+		aplic_syscore_registered = true;
+	}
+}
+
 static int aplic_pm_notifier(struct notifier_block *nb, unsigned long action, void *data)
 {
 	struct aplic_priv *priv = container_of(nb, struct aplic_priv, genpd_nb);
@@ -379,7 +389,7 @@ static int aplic_probe(struct platform_device *pdev)
 		return rc;
 	}
 
-	register_syscore(&aplic_syscore);
+	aplic_syscore_init();
 
 #ifdef CONFIG_ACPI
 	if (!acpi_disabled)