usb: xhci: tegra: mark PM functions as __maybe_unused

The added #ifdefs in the PM rework were almost correct, but still
cause warnings in some randconfig builds:

drivers/usb/host/xhci-tegra.c:2147:12: error: 'tegra_xusb_resume' defined but not used [-Werror=unused-function]
2147 | static int tegra_xusb_resume(struct device *dev)
| ^~~~~~~~~~~~~~~~~
drivers/usb/host/xhci-tegra.c:2105:12: error: 'tegra_xusb_suspend' defined but not used [-Werror=unused-function]
2105 | static int tegra_xusb_suspend(struct device *dev)

Replace the #ifdef checks with simpler __maybe_unused annotations to
reliably shut up these warnings.

Link: https://lore.kernel.org/all/[e-mail]/
Fixes: 971ee247060d ("usb: xhci: tegra: Enable ELPG for runtime/system PM")
Reviewed-by: JC Kuo <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/host/xhci-tegra.c

···
 	return 0;
 }
 
-#if IS_ENABLED(CONFIG_PM) || IS_ENABLED(CONFIG_PM_SLEEP)
 static bool xhci_hub_ports_suspended(struct xhci_hub *hub)
 {
 	struct device *dev = hub->hcd->self.controller;
···
 	return err;
 }
 
-static int tegra_xusb_suspend(struct device *dev)
+static __maybe_unused int tegra_xusb_suspend(struct device *dev)
 {
 	struct tegra_xusb *tegra = dev_get_drvdata(dev);
 	int err;
···
 	return err;
 }
 
-static int tegra_xusb_resume(struct device *dev)
+static __maybe_unused int tegra_xusb_resume(struct device *dev)
 {
 	struct tegra_xusb *tegra = dev_get_drvdata(dev);
 	int err;
···
 
 	return 0;
 }
-#endif
 
-#ifdef CONFIG_PM
-static int tegra_xusb_runtime_suspend(struct device *dev)
+static __maybe_unused int tegra_xusb_runtime_suspend(struct device *dev)
 {
 	struct tegra_xusb *tegra = dev_get_drvdata(dev);
 	int ret;
···
 	return ret;
 }
 
-static int tegra_xusb_runtime_resume(struct device *dev)
+static __maybe_unused int tegra_xusb_runtime_resume(struct device *dev)
 {
 	struct tegra_xusb *tegra = dev_get_drvdata(dev);
 	int err;
···
 
 	return err;
 }
-#endif
 
 static const struct dev_pm_ops tegra_xusb_pm_ops = {
 	SET_RUNTIME_PM_OPS(tegra_xusb_runtime_suspend,