irqchip/renesas-rzg2l: Replace single irq_chip with per-region irq_chip instances

irqchip/renesas-rzg2l: Replace single irq_chip with per-region irq_chip instances

The driver uses a single irq_chip instance shared across all interrupt
types, relying on dispatcher callbacks to differentiate between IRQ and
TINT regions at runtime.

Replace the per-SoC irq_chip and its dispatcher callbacks with dedicated
irq_chip instances for each interrupt region: IRQ and TINT. Subsequent
patches will add per-region callbacks for IRQ and TINT from the common
code.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260325192451.172562-6-biju.das.jz@bp.renesas.com