ASoC: stm32: fix dtbs_check warnings

Merge series from Olivier Moysan <olivier.moysan@foss.st.com>:

Fix dtbs_check warnings in STM32MP15 DK boards Devices Trees for
STM32 I2S and Cirrus CS42L51 codec.

- Add OF graph port property in I2S and CS42L51 DT bindings.
  Fixes warnings:
  audio-controller@4000b000: Unevaluated properties are not allowed
  ('port' was unexpected)
  cs42l51@4a: Unevaluated properties are not allowed
  ('port' was unexpected)
- Correct OF graph DAI audio format property for STM32MP15x Dkx I2S node

Documentation/devicetree/bindings/sound/cirrus,cs42l51.yaml

@@ -44,6 +44,10 @@ properties:
   VAHP-supply:
     description: phandle to voltage regulator of headphone
 
+  port:
+    $ref: audio-graph-port.yaml#
+    unevaluatedProperties: false
+
 required:
   - compatible
   - reg
@@ -69,6 +73,13 @@ examples:
         VA-supply = <&reg_audio>;
         VAHP-supply = <&reg_audio>;
         reset-gpios = <&gpiog 9 GPIO_ACTIVE_LOW>;
+
+        /* assume audio-graph */
+        port {
+          cpu_endpoint: endpoint {
+            remote-endpoint = <&cpu_endpoint>;
+          };
+        };
       };
     };
 ...

Documentation/devicetree/bindings/sound/st,stm32-i2s.yaml

@@ -61,6 +61,10 @@ properties:
     description: Configure the I2S device as MCLK clock provider.
     const: 0
 
+  port:
+    $ref: audio-graph-port.yaml#
+    unevaluatedProperties: false
+
 required:
   - compatible
   - "#sound-dai-cells"
@@ -89,6 +93,13 @@ examples:
         dma-names = "rx", "tx";
         pinctrl-names = "default";
         pinctrl-0 = <&i2s2_pins_a>;
+
+        /* assume audio-graph */
+        port {
+            codec_endpoint: endpoint {
+                remote-endpoint = <&codec_endpoint>;
+            };
+        };
     };
 
 ...