ASoC: dt-bindings: ep93xx: Document DMA support

Document DMA support in binding document.

Signed-off-by: Nikita Shubin <nikita.shubin@maquefel.me>
Tested-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/devicetree/bindings/sound/cirrus,ep9301-i2s.yaml

@@ -40,6 +40,16 @@ properties:
       - const: sclk
       - const: lrclk
 
+  dmas:
+    items:
+      - description: out DMA channel
+      - description: in DMA channel
+
+  dma-names:
+    items:
+      - const: tx
+      - const: rx
+
 required:
   - compatible
   - '#sound-dai-cells'
@@ -61,6 +71,8 @@ examples:
                  <&syscon 30>,
                  <&syscon 31>;
         clock-names = "mclk", "sclk", "lrclk";
+        dmas = <&dma0 0 1>, <&dma0 0 2>;
+        dma-names = "tx", "rx";
     };
 
 ...