ARM: dts: vf610-zii-dev: enable vf610 builtin temp sensor

Vybrid has single internal temperature sensor connected to both internal
ADC modules.

vf610-zii-dev already has ADC0 enabled. Now, to get temperature sensor
captured by iio_hwmon driver, need to configure iio_hwmon node to use
that ADC.

Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Acked-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>