dts: bindings: dac: Change the property names in the overlay

Change the property names in the bindings and overlay
to use hyphens(-) for separation instead of underscores(_).

Signed-off-by: James Roy <[email protected]>

Author: rruuaanng

dts/bindings/dac/microchip,mcp4728.yaml

@@ -8,7 +8,7 @@ properties:
   "#io-channel-cells":
     const: 1
 
-  voltage_reference:
+  voltage-reference:
     type: array
     required: true
     description: |
@@ -17,7 +17,7 @@ properties:
       1 - Internal voltage reference (2.048V)
       Note: array entries correspond to the successive channels
 
-  power_down_mode:
+  power-down-mode:
     type: array
     required: true
     description: |

tests/drivers/build_all/dac/app.overlay

@@ -65,8 +65,8 @@
 				compatible = "microchip,mcp4728";
 				reg = <0x61>;
 				#io-channel-cells = <1>;
-				voltage_reference = <0>;
-				power_down_mode = <0>;
+				voltage-reference = <0>;
+				power-down-mode = <0>;
 			};
 
 			test_i2c_dacx0501:dacx0501@62 {