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.