drm/exynos: fix building without CONFIG_PM_SLEEP

The runtime PM operations use the suspend/resume functions
even when CONFIG_PM_SLEEP is not set, but this now fails
for the exynos DRM driver:

exynos_mixer.c:1289:61: error: 'exynos_mixer_resume' undeclared here (not in a function)
  SET_RUNTIME_PM_OPS(exynos_mixer_suspend, exynos_mixer_resume, NULL)

This removes the #ifdef and instead marks the functions as
__maybe_unused, which does the right thing in all cases and
also looks nicer.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_mixer.c

@@ -1289,8 +1289,7 @@ static int mixer_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM_SLEEP
-static int exynos_mixer_suspend(struct device *dev)
+static int __maybe_unused exynos_mixer_suspend(struct device *dev)
 {
 	struct mixer_context *ctx = dev_get_drvdata(dev);
 	struct mixer_resources *res = &ctx->mixer_res;
@@ -1306,7 +1305,7 @@ static int exynos_mixer_suspend(struct device *dev)
 	return 0;
 }
 
-static int exynos_mixer_resume(struct device *dev)
+static int __maybe_unused exynos_mixer_resume(struct device *dev)
 {
 	struct mixer_context *ctx = dev_get_drvdata(dev);
 	struct mixer_resources *res = &ctx->mixer_res;
@@ -1342,7 +1341,6 @@ static int exynos_mixer_resume(struct device *dev)
 
 	return 0;
 }
-#endif
 
 static const struct dev_pm_ops exynos_mixer_pm_ops = {
 	SET_RUNTIME_PM_OPS(exynos_mixer_suspend, exynos_mixer_resume, NULL)