ARM: dts: at91: sama5d3_xplained: fix ADC vref

The voltage reference for the ADC is not 3V but 3.3V since it is connected to
VDDANA.
Signed-off-by: NLudovic Desroches <ludovic.desroches@microchip.com>
Cc: <stable@vger.kernel.org> # 3.16+
Acked-by: NNicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

arch/arm/boot/dts/at91-sama5d3_xplained.dts

@@ -162,6 +162,7 @@
 			};
 
 			adc0: adc@f8018000 {
+				atmel,adc-vref = <3300>;
 				pinctrl-0 = <
 					&pinctrl_adc0_adtrg
 					&pinctrl_adc0_ad0