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

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 <liu.xuemei1@zte.com.cn>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260331093029749vRpdH-0qoEqjS0Wnn9M4x@zte.com.cn