iio: adc: meson: fix core clock enable/disable moment

iio: adc: meson: fix core clock enable/disable moment

Enable core clock at probe stage and disable it at remove stage.
Core clock is responsible for turning on/off the entire SoC module so
it should be on before the first module register is touched and be off
at very last moment.

Fixes: 3adbf3427330 ("iio: adc: add a driver for the SAR ADC found in Amlogic Meson SoCs")
Signed-off-by: George Stark <gnstark@sberdevices.ru>
Link: https://lore.kernel.org/r/20230721102413.255726-2-gnstark@sberdevices.ru
Cc: <stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>