The AT91 SoCs often embeds an ADC. This patch adds the needed
platform data to specify the informations required by the driver
to work properly.

For now, we only need the reference voltage and which channels
are available on the board.
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: NNicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: NJonathan Cameron <jic23@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>