amba: tegra-ahb: Mark PM functions as __maybe_unused

clang warns about an unused variable when CONFIG_PM is disabled, since
it is only referenced from an #ifdef:

drivers/amba/tegra-ahb.c:97:18: error: variable 'tegra_ahb_gizmo' is not needed and will not be emitted [-Werror,-Wunneeded-internal-declaration]

Rather than trying to get the #ifdef right, remove it and use
__maybe_unused here, which is less error prone.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/amba/tegra-ahb.c

@@ -170,8 +170,7 @@ int tegra_ahb_enable_smmu(struct device_node *dn)
 EXPORT_SYMBOL(tegra_ahb_enable_smmu);
 #endif
 
-#ifdef CONFIG_PM
-static int tegra_ahb_suspend(struct device *dev)
+static int __maybe_unused tegra_ahb_suspend(struct device *dev)
 {
 	int i;
 	struct tegra_ahb *ahb = dev_get_drvdata(dev);
@@ -181,7 +180,7 @@ static int tegra_ahb_suspend(struct device *dev)
 	return 0;
 }
 
-static int tegra_ahb_resume(struct device *dev)
+static int __maybe_unused tegra_ahb_resume(struct device *dev)
 {
 	int i;
 	struct tegra_ahb *ahb = dev_get_drvdata(dev);
@@ -190,7 +189,6 @@ static int tegra_ahb_resume(struct device *dev)
 		gizmo_writel(ahb, ahb->ctx[i], tegra_ahb_gizmo[i]);
 	return 0;
 }
-#endif
 
 static UNIVERSAL_DEV_PM_OPS(tegra_ahb_pm,
 			    tegra_ahb_suspend,