power: supply: max17042_battery: Fix compiler warning

Fix drivers/power/supply/max17042_battery.c:1059:6:
warning: 'acpi_id' may be used uninitialized in this function.

No idea why my gcc version did not catch this.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

drivers/power/supply/max17042_battery.c

@@ -983,7 +983,7 @@ static int max17042_probe(struct i2c_client *client,
 	struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
 	const struct power_supply_desc *max17042_desc = &max17042_psy_desc;
 	struct power_supply_config psy_cfg = {};
-	const struct acpi_device_id *acpi_id;
+	const struct acpi_device_id *acpi_id = NULL;
 	struct device *dev = &client->dev;
 	struct max17042_chip *chip;
 	int ret;