iio: adc: mediatek: mt6577-auxadc, add mt6765 support

1. Add calibrated sample data support
2. Use of_match_table to decide each platform's
   feature set

Signed-off-by: Chun-Hung Wu <chun-hung.wu@mediatek.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>