iio: adc: ad7380: use devm_regulator_get_enable_read_voltage()

Use devm_regulator_get_enable_read_voltage() to simplify the code.

Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Julien Stephan <jstephan@baylibre.com>
Link: https://patch.msgid.link/20241022-ad7380-fix-supplies-v3-2-f0cefe1b7fa6@baylibre.com


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