ARM: at91/dt: at91-ariag25: remove useless adc properties

Remove the properties that are not used anymore by the at91_adc driver.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/at91-ariag25.dts

@@ -129,7 +129,6 @@ uart1: serial@f8044000 {
 			adc0: adc@f804c000 {
 				status = "okay";
 				atmel,adc-channels-used = <0xf>;
-				atmel,adc-num-channels = <4>;
 			};
 
 			dbgu: serial@fffff200 {