spi: lpspi: add dmas property

The LPSPI has dma capability, so add dma property.

Signed-off-by: Peng Fan <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

Documentation/devicetree/bindings/spi/spi-fsl-lpspi.yaml

···
       - const: per
       - const: ipg
 
+  dmas:
+    items:
+      - description: TX DMA Channel
+      - description: RX DMA Channel
+
+  dma-names:
+    items:
+      - const: tx
+      - const: rx
+
   fsl,spi-only-use-cs1-sel:
     description:
       spi common code does not support use of CS signals discontinuously.