iio: adc: exynos-adc: Add S5PV210 variant

S5PV210's ADC variant is almost the same as v1 except that it has 10
channels and doesn't require the pmu register

Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>