hwmon: Convert mc13783-adc to mc13xxx API

The mc13783_... functions are going to be removed, so switch to the
more generic API.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>