iio: exynos_adc: do a soft reset in case of timeout

Do a soft reset software if a timeout happens.
This is applicable only for ADC_V2.

Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@samsung.com>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>