irqchip: Add StarFive external interrupt controller

Add StarFive external interrupt controller for JH8100 SoC.

Signed-off-by: Changhuang Liang <changhuang.liang@starfivetech.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ley Foon Tan <leyfoon.tan@starfivetech.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20240226055025.1669223-3-changhuang.liang@starfivetech.com