slimbus: ngd: mark PM functions as __maybe_unused

qcom_slim_ngd_runtime_suspend is protected by an #ifdef,
qcom_slim_ngd_runtime_idle is now, which causes a build time warning:

drivers/slimbus/qcom-ngd-ctrl.c:1470:12: error: 'qcom_slim_ngd_runtime_idle' defined but not used [-Werror=unused-function]

Marking both as __maybe_unused lets us get rid of the warning
as well as the #ifdef.

Fixes: 917809e228 ("slimbus: ngd: Add qcom SLIMBus NGD driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/slimbus/qcom-ngd-ctrl.c

@@ -1467,7 +1467,7 @@ static int qcom_slim_ngd_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static int qcom_slim_ngd_runtime_idle(struct device *dev)
+static int __maybe_unused qcom_slim_ngd_runtime_idle(struct device *dev)
 {
 	struct qcom_slim_ngd_ctrl *ctrl = dev_get_drvdata(dev);
 
@@ -1477,8 +1477,7 @@ static int qcom_slim_ngd_runtime_idle(struct device *dev)
 	return -EAGAIN;
 }
 
-#ifdef CONFIG_PM
-static int qcom_slim_ngd_runtime_suspend(struct device *dev)
+static int __maybe_unused qcom_slim_ngd_runtime_suspend(struct device *dev)
 {
 	struct qcom_slim_ngd_ctrl *ctrl = dev_get_drvdata(dev);
 	int ret = 0;
@@ -1491,7 +1490,6 @@ static int qcom_slim_ngd_runtime_suspend(struct device *dev)
 
 	return ret;
 }
-#endif
 
 static const struct dev_pm_ops qcom_slim_ngd_dev_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,