iio:magn:mag3110: Switch from CONFIG_PM_SLEEP guards to pm_sleep_ptr() etc

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>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20220130193147.279148-31-jic23@kernel.org

drivers/iio/magnetometer/mag3110.c

@@ -573,7 +573,6 @@ static int mag3110_remove(struct i2c_client *client)
 	return 0;
 }
 
-#ifdef CONFIG_PM_SLEEP
 static int mag3110_suspend(struct device *dev)
 {
 	struct mag3110_data *data = iio_priv(i2c_get_clientdata(
@@ -623,11 +622,8 @@ static int mag3110_resume(struct device *dev)
 		data->ctrl_reg1);
 }
 
-static SIMPLE_DEV_PM_OPS(mag3110_pm_ops, mag3110_suspend, mag3110_resume);
-#define MAG3110_PM_OPS (&mag3110_pm_ops)
-#else
-#define MAG3110_PM_OPS NULL
-#endif
+static DEFINE_SIMPLE_DEV_PM_OPS(mag3110_pm_ops, mag3110_suspend,
+				mag3110_resume);
 
 static const struct i2c_device_id mag3110_id[] = {
 	{ "mag3110", 0 },
@@ -645,7 +641,7 @@ static struct i2c_driver mag3110_driver = {
 	.driver = {
 		.name	= "mag3110",
 		.of_match_table = mag3110_of_match,
-		.pm	= MAG3110_PM_OPS,
+		.pm	= pm_sleep_ptr(&mag3110_pm_ops),
 	},
 	.probe = mag3110_probe,
 	.remove = mag3110_remove,