usb: dwc3: pci: fix build warning on !PM_SLEEP

When building a kernel with CONFIG_PM_SLEEP=n, we
get the following warning:

drivers/usb/dwc3/dwc3-pci.c:253:12: warning: 'dwc3_pci_pm_dummy' defined but not used

In order to fix this, we should only define
dwc3_pci_pm_dummy() when CONFIG_PM_SLEEP is defined.

Fixes: f6c274e11e3b ("usb: dwc3: pci: runtime_resume child device")
Reported-by: Arnd Bergmann <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/dwc3/dwc3-pci.c

···
 
 	return pm_runtime_get(&dwc3->dev);
 }
+#endif /* CONFIG_PM */
 
+#ifdef CONFIG_PM_SLEEP
 static int dwc3_pci_pm_dummy(struct device *dev)
 {
 	/*
···
 	 */
 	return 0;
 }
-#endif /* CONFIG_PM */
+#endif /* CONFIG_PM_SLEEP */
 
 static struct dev_pm_ops dwc3_pci_dev_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(dwc3_pci_pm_dummy, dwc3_pci_pm_dummy)