ASoC: dt-bindings: nau8821: Add DMIC slew rate.

Add input with DMIC slew rate controls.
Signed-off-by: Seven Lee <wtli@nuvoton.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231107035230.1241683-2-wtli@nuvoton.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/nuvoton,nau8821.yaml

@@ -89,6 +89,14 @@ properties:
     $ref: /schemas/types.yaml#/definitions/uint32
     default: 3072000
 
+  nuvoton,dmic-slew-rate:
+    description: The range 0 to 7 represents the speed of DMIC slew rate.
+        The lowest value 0 means the slowest rate and the highest value
+        7 means the fastest rate.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    maximum: 7
+    default: 0
+
   nuvoton,left-input-single-end:
     description: Enable left input with single-ended settings if set.
         For the headset mic application, the single-ended control is
@@ -127,6 +135,7 @@ examples:
             nuvoton,jack-insert-debounce = <7>;
             nuvoton,jack-eject-debounce = <0>;
             nuvoton,dmic-clk-threshold = <3072000>;
+            nuvoton,dmic-slew-rate= <0>;
             #sound-dai-cells = <0>;
         };
     };