ASoC: rockchip-i2s: add description for rk3308

The description below is already in use for rk3308.dtsi,
but was somehow never added to a document, so add
"rockchip,rk3308-i2s", "rockchip,rk3066-i2s"
for i2s nodes on a rk3308 platform to rockchip-i2s.yaml.
One of the rk3308 i2s nodes also has a different dma layout,
so change that as well.
Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/20200507113238.7904-1-jbx6244@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/rockchip-i2s.yaml

@@ -24,6 +24,7 @@ properties:
             - rockchip,rk3188-i2s
             - rockchip,rk3228-i2s
             - rockchip,rk3288-i2s
+            - rockchip,rk3308-i2s
             - rockchip,rk3328-i2s
             - rockchip,rk3366-i2s
             - rockchip,rk3368-i2s
@@ -47,14 +48,15 @@ properties:
       - const: i2s_hclk
 
   dmas:
-    items:
-      - description: TX DMA Channel
-      - description: RX DMA Channel
+    minItems: 1
+    maxItems: 2
 
   dma-names:
-    items:
-      - const: tx
+    oneOf:
       - const: rx
+      - items:
+        - const: tx
+        - const: rx
 
   power-domains:
     maxItems: 1