dt-bindings: input: ti-tsc-adc: Add new compatible for AM654 SoCs

AM654 SoCs has ADC IP which is similar to AM335x, but without the
touchscreen part. Add new compatible to handle AM654 SoCs. Also, it
seems that existing compatible strings used in the kernel DTs were never
documented. So, document them now.
Signed-off-by: Vignesh R <vigneshr@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>

Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt

@@ -2,7 +2,12 @@
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Required properties:
+- mfd
+	compatible: Should be
+		"ti,am3359-tscadc" for AM335x/AM437x SoCs
+		"ti,am654-tscadc", "ti,am3359-tscadc" for AM654 SoCs
 - child "tsc"
+	compatible: Should be "ti,am3359-tsc".
 	ti,wires: Wires refer to application modes i.e. 4/5/8 wire touchscreen
 		  support on the platform.
 	ti,x-plate-resistance: X plate resistance
@@ -25,6 +30,9 @@ Required properties:
 			AIN0 = 0, AIN1 = 1 and so on till AIN7 = 7.
 			XP  = 0, XN = 1, YP = 2, YN = 3.
 - child "adc"
+	compatible: Should be
+		    "ti,am3359-adc" for AM335x/AM437x SoCs
+		    "ti,am654-adc", "ti,am3359-adc" for AM654 SoCs
 	ti,adc-channels: List of analog inputs available for ADC.
 			 AIN0 = 0, AIN1 = 1 and so on till AIN7 = 7.