ARM: dts: Cygnus: Drop incorrect io-channel-ranges property.

This property applies to consumers of io-channels. In this case we
have a provider so the property is not used.

Recent changes to dt-schema result int his being reported as an error
as a dependency is enforced between this property and io-channels.

Signed-off-by: Jonathan Cameron <[e-mail]>
Cc: Florian Fainelli <[e-mail]>
Signed-off-by: Florian Fainelli <[e-mail]>

arch/arm/boot/dts/bcm-cygnus.dtsi

···
 		adc: adc@180a6000 {
 			compatible = "brcm,iproc-static-adc";
 			#io-channel-cells = <1>;
-			io-channel-ranges;
 			adc-syscon = <&ts_adc_syscon>;
 			clocks = <&asiu_clks BCM_CYGNUS_ASIU_ADC_CLK>;
 			clock-names = "tsc_clk";