commit 9cdd31e5 upstream.

The voltage reference for the ADC is not 3V but 3.3V since it is connected to
VDDANA.
Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>