usb: dwc3: qcom: mark PM functions as __maybe_unused

The #ifdef guards around these are wrong, resulting in warnings
in certain configurations:

drivers/usb/dwc3/dwc3-qcom.c:244:12: error: 'dwc3_qcom_resume' defined but not used [-Werror=unused-function]
static int dwc3_qcom_resume(struct dwc3_qcom *qcom)
^~~~~~~~~~~~~~~~
drivers/usb/dwc3/dwc3-qcom.c:223:12: error: 'dwc3_qcom_suspend' defined but not used [-Werror=unused-function]
static int dwc3_qcom_suspend(struct dwc3_qcom *qcom)

This replaces the guards with __maybe_unused annotations to shut up
the warnings and give better compile time coverage.

Fixes: a4333c3a6ba9 ("usb: dwc3: Add Qualcomm DWC3 glue driver")
Reviewed-by: Douglas Anderson <[e-mail]>
Acked-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/dwc3/dwc3-qcom.c

···
 	return 0;
 }
 
-#ifdef CONFIG_PM_SLEEP
-static int dwc3_qcom_pm_suspend(struct device *dev)
+static int __maybe_unused dwc3_qcom_pm_suspend(struct device *dev)
 {
 	struct dwc3_qcom *qcom = dev_get_drvdata(dev);
 	int ret = 0;
···
 	return ret;
 }
 
-static int dwc3_qcom_pm_resume(struct device *dev)
+static int __maybe_unused dwc3_qcom_pm_resume(struct device *dev)
 {
 	struct dwc3_qcom *qcom = dev_get_drvdata(dev);
 	int ret;
···
 
 	return ret;
 }
-#endif
 
-#ifdef CONFIG_PM
-static int dwc3_qcom_runtime_suspend(struct device *dev)
+static int __maybe_unused dwc3_qcom_runtime_suspend(struct device *dev)
 {
 	struct dwc3_qcom *qcom = dev_get_drvdata(dev);
 
 	return dwc3_qcom_suspend(qcom);
 }
 
-static int dwc3_qcom_runtime_resume(struct device *dev)
+static int __maybe_unused dwc3_qcom_runtime_resume(struct device *dev)
 {
 	struct dwc3_qcom *qcom = dev_get_drvdata(dev);
 
 	return dwc3_qcom_resume(qcom);
 }
-#endif
 
 static const struct dev_pm_ops dwc3_qcom_dev_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(dwc3_qcom_pm_suspend, dwc3_qcom_pm_resume)