media: renesas-ceu: mark PM functions as __maybe_unused

The PM runtime operations are unused when CONFIG_PM is disabled,
leading to a harmless warning:

drivers/media/platform/renesas-ceu.c:1003:12: error: 'ceu_runtime_suspend' defined but not used [-Werror=unused-function]
 static int ceu_runtime_suspend(struct device *dev)
            ^~~~~~~~~~~~~~~~~~~
drivers/media/platform/renesas-ceu.c:987:12: error: 'ceu_runtime_resume' defined but not used [-Werror=unused-function]
 static int ceu_runtime_resume(struct device *dev)
            ^~~~~~~~~~~~~~~~~~

This adds a __maybe_unused annotation to shut up the warning.

Fixes: 32e5a70d ("media: platform: Add Renesas CEU driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/renesas-ceu.c

@@ -984,7 +984,7 @@ static int ceu_init_mbus_fmt(struct ceu_device *ceudev)
 /*
  * ceu_runtime_resume() - soft-reset the interface and turn sensor power on.
  */
-static int ceu_runtime_resume(struct device *dev)
+static int __maybe_unused ceu_runtime_resume(struct device *dev)
 {
 	struct ceu_device *ceudev = dev_get_drvdata(dev);
 	struct v4l2_subdev *v4l2_sd = ceudev->sd->v4l2_sd;
@@ -1000,7 +1000,7 @@ static int ceu_runtime_resume(struct device *dev)
  * ceu_runtime_suspend() - disable capture and interrupts and soft-reset.
  *			   Turn sensor power off.
  */
-static int ceu_runtime_suspend(struct device *dev)
+static int __maybe_unused ceu_runtime_suspend(struct device *dev)
 {
 	struct ceu_device *ceudev = dev_get_drvdata(dev);
 	struct v4l2_subdev *v4l2_sd = ceudev->sd->v4l2_sd;