ARM: dts: aspeed: cmm: enable iio-hwmon-adc

Bind aspeed ADC channels 0-7 to "iio-hwmon" driver so the data of these
voltage sensing channels can be accessed by "lm_sensors". Channels 8-15
are not used on CMM BMC.
Signed-off-by: Tao Ren <taoren@fb.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>

arch/arm/boot/dts/aspeed-bmc-facebook-cmm.dts

@@ -56,6 +56,12 @@ chosen {
 	memory@80000000 {
 		reg = <0x80000000 0x20000000>;
 	};
+
+	ast-adc-hwmon {
+		compatible = "iio-hwmon";
+		io-channels = <&adc 0>, <&adc 1>, <&adc 2>, <&adc 3>,
+			      <&adc 4>, <&adc 5>, <&adc 6>, <&adc 7>;
+	};
 };
 
 &pinctrl {