spi: dt-bindings: renesas,rzv2h-rspi: allow multiple DMAs

All supported SoCs have multiple DMA controllers that can be used with
the RSPI peripheral. The current bindings only allow a single pair of RX
and TX DMAs.

The DMA core allows specifying multiple DMAs with the same name, and it
will pick the first available one.

There is an exception in the base dt-schema rules specifically for
allowing this behavior (dtschema/schemas/dma/dma.yaml).

dma-names:
anyOf:
- uniqueItems: true
- items:
# Hack around Renesas bindings which repeat entries to support
# multiple possible DMA providers
enum: [rx, tx]

Allow multiple DMAs to have the same name and only restrict the possible
names of the DMA channels, not their count.

For RZ/T2H and RZ/N2H SoCs, limit the number of DMA channels to 6, as
they have 3 DMA controllers.

For RZ/V2H and RZ/V2N SoCs, limit the number of DMA channels to 10, as
they have 5 DMA controllers.

Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20260128215132.1353381-2-cosmin-gabriel.tanislav.xa@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>