iio: adc: ad7606: simplify using devm_regulator_get_enable()

Drop open-coded pattern: 'devm_regulator_get(), regulator_enable(),
add_action_or_reset(regulator_disable)' and use the
devm_regulator_get_enable() and drop the pointer to the regulator.
This simplifies code and makes it less tempting to add manual control
for the regulator which is also controlled by devm.

Whilst here also switch to dev_err_probe() to provide more information
if a deferred probe occurs.

Signed-off-by: Matti Vaittinen <[e-mail]>
Acked-by: Nuno Sá <[e-mail]>
Link: https://lore.kernel.org/r/521c52[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/ad7606.c

···
 	.validate_device = iio_trigger_validate_own_device,
 };
 
-static void ad7606_regulator_disable(void *data)
-{
-	struct ad7606_state *st = data;
-
-	regulator_disable(st->reg);
-}
-
 int ad7606_probe(struct device *dev, int irq, void __iomem *base_address,
 		 const char *name, unsigned int id,
 		 const struct ad7606_bus_ops *bops)
···
 	st->scale_avail = ad7606_scale_avail;
 	st->num_scales = ARRAY_SIZE(ad7606_scale_avail);
 
-	st->reg = devm_regulator_get(dev, "avcc");
-	if (IS_ERR(st->reg))
-		return PTR_ERR(st->reg);
-
-	ret = regulator_enable(st->reg);
-	if (ret) {
-		dev_err(dev, "Failed to enable specified AVcc supply\n");
-		return ret;
-	}
-
-	ret = devm_add_action_or_reset(dev, ad7606_regulator_disable, st);
+	ret = devm_regulator_get_enable(dev, "avcc");
 	if (ret)
-		return ret;
+		return dev_err_probe(dev, ret,
+				     "Failed to enable specified AVcc supply\n");
 
 	st->chip_info = &ad7606_chip_info_tbl[id];
 

drivers/iio/adc/ad7606.h

···
  * struct ad7606_state - driver instance specific data
  * @dev		pointer to kernel device
  * @chip_info		entry in the table of chips that describes this device
- * @reg		regulator info for the power supply of the device
  * @bops		bus operations (SPI or parallel)
  * @range		voltage range selection, selects which scale to apply
  * @oversampling	oversampling selection
···
 struct ad7606_state {
 	struct device			*dev;
 	const struct ad7606_chip_info	*chip_info;
-	struct regulator		*reg;
 	const struct ad7606_bus_ops	*bops;
 	unsigned int			range[16];
 	unsigned int			oversampling;