dmaengine: sh: rz_dmac: make register_dma_req() chip-specific

dmaengine: sh: rz_dmac: make register_dma_req() chip-specific

The Renesas RZ/T2H (R9A09G077) and RZ/N2H (R9A09G087) SoCs use a
completely different ICU unit compared to RZ/V2H, which requires a
separate implementation.

To prepare for adding support for these SoCs, add a chip-specific
structure and put a pointer to the rzv2h_icu_register_dma_req() function
in the .register_dma_req field of the chip-specific structure to allow
for other implementations. Do the same for the default request value,
RZV2H_ICU_DMAC_REQ_NO_DEFAULT, and place it into .dma_req_no_default.

While at it, factor out the logic that calls .register_dma_req() or
rz_dmac_set_dmars_register() into a separate function to remove some
code duplication.

Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20260105114445.878262-3-cosmin-gabriel.tanislav.xa@renesas.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>