rtc: max77686: convert to i2c_new_ancillary_device

Convert RTC I2C device creation from devm_i2c_new_dummy_device() to
i2c_new_ancillary_device() to enable the use of a device tree-specified
RTC address instead of a hardcoded value. If the device tree does not
provide an address, use hardcoded values as a fallback.

This addresses an issue with the MAX77663 PMIC, which can have the RTC at
different I2C positions (either 0x48, like the MAX77714, or 0x68, like
the MAX77620). The MAX77620 value is used as the default. The I2C position
of the MAX77663 is factory-set and cannot be detected from the chip
itself.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Link: https://patch.msgid.link/20260312085258.11431-6-clamor95@gmail.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Author: clamor-s

drivers/rtc/rtc-max77686.c

@@ -686,6 +686,11 @@ static int max77686_rtc_init_reg(struct max77686_rtc_info *info)
 	return ret;
 }
 
+static void max77686_rtc_release_dev(void *client)
+{
+	i2c_unregister_device(client);
+}
+
 static int max77686_init_rtc_regmap(struct max77686_rtc_info *info)
 {
 	struct device *parent = info->dev->parent;
@@ -713,12 +718,17 @@ static int max77686_init_rtc_regmap(struct max77686_rtc_info *info)
 		goto add_rtc_irq;
 	}
 
-	client = devm_i2c_new_dummy_device(info->dev, parent_i2c->adapter,
-					   info->drv_data->rtc_i2c_addr);
+	client = i2c_new_ancillary_device(parent_i2c, "rtc",
+					  info->drv_data->rtc_i2c_addr);
 	if (IS_ERR(client))
 		return dev_err_probe(info->dev, PTR_ERR(client),
 				     "Failed to allocate I2C device for RTC\n");
 
+	ret = devm_add_action_or_reset(info->dev, max77686_rtc_release_dev,
+				       client);
+	if (ret)
+		return ret;
+
 	info->rtc_regmap = devm_regmap_init_i2c(client,
 						info->drv_data->regmap_config);
 	if (IS_ERR(info->rtc_regmap))