irqchip/sifive-plic: Add ACPI support

Add ACPI support in PLIC driver. Use the mapping created early during
boot to get details about the PLIC.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Co-developed-by: Haibo Xu <haibo1.xu@intel.com>
Signed-off-by: Haibo Xu <haibo1.xu@intel.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://patch.msgid.link/20240812005929.113499-18-sunilvl@ventanamicro.com


[ rjw: Rebase on top of recent irqchip changes ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>