dt-bindings: touchscreen: move ar1021.txt to trivial-touch.yaml

ar1021 have only reg and interrupts property beside touch common
properties. So move context of ar1021.txt into trivial-touch.yaml.

Signed-off-by: Frank Li <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

Documentation/devicetree/bindings/input/touchscreen/ar1021.txt

···
-* Microchip AR1020 and AR1021 touchscreen interface (I2C)
-
-Required properties:
-- compatible		: "microchip,ar1021-i2c"
-- reg			: I2C slave address
-- interrupts		: touch controller interrupt
-
-Example:
-
-	touchscreen@4d {
-		compatible = "microchip,ar1021-i2c";
-		reg = <0x4d>;
-		interrupt-parent = <&gpio3>;
-		interrupts = <11 IRQ_TYPE_LEVEL_HIGH>;
-	};

Documentation/devicetree/bindings/input/touchscreen/trivial-touch.yaml

···
     enum:
       # MAXI MAX11801 Resistive touch screen controller with i2c interface
       - maxim,max11801
+      # Microchip AR1020 and AR1021 touchscreen interface (I2C)
+      - microchip,ar1021-i2c
 
   reg:
     maxItems: 1