spi: dt-bindings: renesas,rzv2h-rspi: document optional support for DMA

The IP supports using DMA for reading and writing data from the FIFO,
document it.

Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20251201134229.600817-11-cosmin-gabriel.tanislav.xa@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Demon000

Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml

@@ -57,6 +57,14 @@ properties:
       - const: presetn
       - const: tresetn
 
+  dmas:
+    maxItems: 2
+
+  dma-names:
+    items:
+      - const: rx
+      - const: tx
+
   power-domains:
     maxItems: 1