iio: magn/ak8974: avoid unused function warning

The ak8974_configure() function is used only from the PM code,
but that can be hidden when CONFIG_PM is disabled:

drivers/iio/magnetometer/ak8974.c:201:12: error: 'ak8974_configure' defined but not used [-Werror=unused-function]

This replaces the #ifdef with a __maybe_unused annotation, which
will work correctly in all configurations and avoid the warning,
as the compiler can now see where ak8974_configure is called from.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 7c94a8b2 ("iio: magn: add a driver for AK8974")
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/magnetometer/ak8974.c

@@ -783,8 +783,7 @@ static int __exit ak8974_remove(struct i2c_client *i2c)
 	return 0;
 }
 
-#ifdef CONFIG_PM
-static int ak8974_runtime_suspend(struct device *dev)
+static int __maybe_unused ak8974_runtime_suspend(struct device *dev)
 {
 	struct ak8974 *ak8974 =
 		iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
@@ -795,7 +794,7 @@ static int ak8974_runtime_suspend(struct device *dev)
 	return 0;
 }
 
-static int ak8974_runtime_resume(struct device *dev)
+static int __maybe_unused ak8974_runtime_resume(struct device *dev)
 {
 	struct ak8974 *ak8974 =
 		iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
@@ -822,7 +821,6 @@ static int ak8974_runtime_resume(struct device *dev)
 
 	return ret;
 }
-#endif /* CONFIG_PM */
 
 static const struct dev_pm_ops ak8974_dev_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,