[media] atmel-isc: mark PM functions as __maybe_unused

The newly added atmel-isc driver uses SET_RUNTIME_PM_OPS() to
refer to its suspend/resume functions, causing a warning when
CONFIG_PM is not set:

media/platform/atmel/atmel-isc.c:1477:12: error: 'isc_runtime_resume' defined but not used [-Werror=unused-function]
media/platform/atmel/atmel-isc.c:1467:12: error: 'isc_runtime_suspend' defined but not used [-Werror=unused-function]

This adds __maybe_unused annotations to avoid the warning without
adding an error-prone #ifdef around it.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/atmel/atmel-isc.c

@@ -1470,7 +1470,7 @@ static int atmel_isc_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static int isc_runtime_suspend(struct device *dev)
+static int __maybe_unused isc_runtime_suspend(struct device *dev)
 {
 	struct isc_device *isc = dev_get_drvdata(dev);
 
@@ -1480,7 +1480,7 @@ static int isc_runtime_suspend(struct device *dev)
 	return 0;
 }
 
-static int isc_runtime_resume(struct device *dev)
+static int __maybe_unused isc_runtime_resume(struct device *dev)
 {
 	struct isc_device *isc = dev_get_drvdata(dev);
 	int ret;