irqchip/renesas-rzv2h: Add rzv2h_icu_register_dma_req()

irqchip/renesas-rzv2h: Add rzv2h_icu_register_dma_req()

On the Renesas RZ/V2H(P) family of SoCs, DMAC IPs are connected
to the Interrupt Control Unit (ICU).
For DMA transfers, a request number must be registered with the
ICU, which means that the DMAC driver has to be able to instruct
the ICU driver with the registration of such id.

Export rzv2h_icu_register_dma_req() so that the DMAC driver can
register the DMAC request number.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20250423143422.3747702-4-fabrizio.castro.jz@renesas.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>