powerpc/dts: add device tree entry for W83793 on T4240RDB

The T4240RDB contains a W83793 hardware monitoring chip. Add a device
tree entry to make the driver attach to it, as the i2c-mpc bus driver
dropped support for class-based instantiation of devices a long time
ago.
Signed-off-by: Florian Larysch <fl@n621.de>
Signed-off-by: Scott Wood <oss@buserror.net>

arch/powerpc/boot/dts/fsl/t4240rdb.dts

@@ -125,6 +125,10 @@ flash@0 {
 		};
 
 		i2c@118000 {
+			hwmon@2f {
+				compatible = "winbond,w83793";
+				reg = <0x2f>;
+			};
 			eeprom@52 {
 				compatible = "at24,24c256";
 				reg = <0x52>;