iio:magn:ak8975: Switch from CONFIG_PM guards to pm_ptr() etc

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

Use the new DEFINE_RUNTIME_DEV_PM_OPS() macro to reduce boilerplate.

Removing instances of this approach from IIO also stops them being
copied into new drivers.
Acked-by: Matt Ranostay <matt.ranostay@konsulko.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Albrieux <jonathan.albrieux@gmail.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20220130193147.279148-30-jic23@kernel.org

drivers/iio/magnetometer/ak8975.c

@@ -1033,7 +1033,6 @@ static int ak8975_remove(struct i2c_client *client)
 	return 0;
 }
 
-#ifdef CONFIG_PM
 static int ak8975_runtime_suspend(struct device *dev)
 {
 	struct i2c_client *client = to_i2c_client(dev);
@@ -1074,14 +1073,9 @@ static int ak8975_runtime_resume(struct device *dev)
 
 	return 0;
 }
-#endif /* CONFIG_PM */
 
-static const struct dev_pm_ops ak8975_dev_pm_ops = {
-	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
-				pm_runtime_force_resume)
-	SET_RUNTIME_PM_OPS(ak8975_runtime_suspend,
-			   ak8975_runtime_resume, NULL)
-};
+static DEFINE_RUNTIME_DEV_PM_OPS(ak8975_dev_pm_ops, ak8975_runtime_suspend,
+				 ak8975_runtime_resume, NULL);
 
 static const struct i2c_device_id ak8975_id[] = {
 	{"ak8975", AK8975},
@@ -1113,7 +1107,7 @@ MODULE_DEVICE_TABLE(of, ak8975_of_match);
 static struct i2c_driver ak8975_driver = {
 	.driver = {
 		.name	= "ak8975",
-		.pm = &ak8975_dev_pm_ops,
+		.pm = pm_ptr(&ak8975_dev_pm_ops),
 		.of_match_table = ak8975_of_match,
 		.acpi_match_table = ak_acpi_match,
 	},