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

Remove the properties that are not used anymore by the at91_adc driver.

Cc: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/at91-cosino.dtsi

@@ -64,7 +64,6 @@ i2c0: i2c@f8010000 {
 			};
 
 			adc0: adc@f804c000 {
-				atmel,adc-clock-rate = <1000000>;
 				atmel,adc-ts-wires = <4>;
 				atmel,adc-ts-pressure-threshold = <10000>;
 				status = "okay";

arch/arm/boot/dts/at91-cosino_mega2560.dts

@@ -27,7 +27,6 @@ macb0: ethernet@f802c000 {
 			};
 
 			adc0: adc@f804c000 {
-				atmel,adc-clock-rate = <1000000>;
 				atmel,adc-ts-wires = <4>;
 				atmel,adc-ts-pressure-threshold = <10000>;
 				status = "okay";