dt-bindings: hwmon: (adc128d818) Specify ti,mode property size

By default, cells in DT are 32-bit in size. The driver reads "ti,mode"
using the function of_property_read_u8() which causes the value to be
read incorrectly in little-endian architectures if the size is not
specified.

Make it explicit in the binding documentation that this prorperty must
be set as a 8-bit value.
Signed-off-by: Carlos Menin <menin@carlosaurelio.net>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/devicetree/bindings/hwmon/adc128d818.txt

@@ -26,7 +26,7 @@ Required node properties:
 
 Optional node properties:
 
- - ti,mode:     Operation mode (see above).
+ - ti,mode:     Operation mode (u8) (see above).
 
 
 Example (operation mode 2):
@@ -34,5 +34,5 @@ Example (operation mode 2):
 	adc128d818@1d {
 		compatible = "ti,adc128d818";
 		reg = <0x1d>;
-		ti,mode = <2>;
+		ti,mode = /bits/ 8 <2>;
 	};