iio:light:isl29018: Switch from CONFIG_PM_SLEEP guards to pm_sleep_ptr()

Letting the compiler remove these functions when the kernel is built
without CONFIG_PM_SLEEP support is simpler and less error prone than the
use of #ifdef based config guards.

Removing instances of this approach from IIO also stops them being
copied into new drivers.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Anson Huang <anson.huang@nxp.com>
Cc: Brian Masney <masneyb@onstation.org>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20220130193147.279148-21-jic23@kernel.org

drivers/iio/light/isl29018.c

@@ -784,7 +784,6 @@ static int isl29018_probe(struct i2c_client *client,
 	return devm_iio_device_register(&client->dev, indio_dev);
 }
 
-#ifdef CONFIG_PM_SLEEP
 static int isl29018_suspend(struct device *dev)
 {
 	struct isl29018_chip *chip = iio_priv(dev_get_drvdata(dev));
@@ -830,11 +829,8 @@ static int isl29018_resume(struct device *dev)
 	return err;
 }
 
-static SIMPLE_DEV_PM_OPS(isl29018_pm_ops, isl29018_suspend, isl29018_resume);
-#define ISL29018_PM_OPS (&isl29018_pm_ops)
-#else
-#define ISL29018_PM_OPS NULL
-#endif
+static DEFINE_SIMPLE_DEV_PM_OPS(isl29018_pm_ops, isl29018_suspend,
+				isl29018_resume);
 
 #ifdef CONFIG_ACPI
 static const struct acpi_device_id isl29018_acpi_match[] = {
@@ -866,7 +862,7 @@ static struct i2c_driver isl29018_driver = {
 	.driver	 = {
 			.name = "isl29018",
 			.acpi_match_table = ACPI_PTR(isl29018_acpi_match),
-			.pm = ISL29018_PM_OPS,
+			.pm = pm_sleep_ptr(&isl29018_pm_ops),
 			.of_match_table = isl29018_of_match,
 		    },
 	.probe	 = isl29018_probe,