irqchip/riscv-aplic: Restrict genpd notifier to device tree only

On ACPI systems, the aplic's pm_domain is set to acpi_general_pm_domain,
which provides its own power management callbacks (e.g., runtime_suspend
via acpi_subsys_runtime_suspend).

aplic_pm_add() unconditionally calls dev_pm_genpd_add_notifier() when
dev->pm_domain is non‑NULL, leading to a comparison between runtime_suspend
and genpd_runtime_suspend. This results in the following errors when ACPI
is enabled:

riscv-aplic RSCV0002:00: failed to create APLIC context
riscv-aplic RSCV0002:00: error -ENODEV: failed to setup APLIC in MSI mode

Fix this by checking for dev->of_node before adding or removing the genpd
notifier, ensuring it is only used for device tree based systems.

Fixes: 95a8ddde3660 ("irqchip/riscv-aplic: Preserve APLIC states across suspend/resume")
Signed-off-by: Jessica Liu <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

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

···
 	struct device *dev = priv->dev;
 
 	list_del(&priv->head);
-	if (dev->pm_domain)
+	if (dev->pm_domain && dev->of_node)
 		dev_pm_genpd_remove_notifier(dev);
 }
 
···
 
 	priv->saved_hw_regs.srcs = srcs;
 	list_add(&priv->head, &aplics);
-	if (dev->pm_domain) {
+	if (dev->pm_domain && dev->of_node) {
 		priv->genpd_nb.notifier_call = aplic_pm_notifier;
 		ret = dev_pm_genpd_add_notifier(dev, &priv->genpd_nb);
 		if (ret)