iio: adc: axp20x_adc: Add adc_en1 and adc_en2 to axp_data

Add the register for adc_en1 and adc_en2 to the axp_data struct. This
allows us to specify a different register to enable the adc channels
for different devices such as the AXP717.

Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20240821215456.962564-2-macroalpha82@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>