irqchip/renesas-rzv2h: Drop irqchip from struct rzv2h_icu_priv

irqchip/renesas-rzv2h: Drop irqchip from struct rzv2h_icu_priv

Use rzv2h_icu_chip directly on irq_domain_set_hwirq_and_chip() and drop
the global variable irqchip from struct rzv2h_icu_priv.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/all/20250224131253.134199-4-biju.das.jz@bp.renesas.com