media: camss: mark PM functions as __maybe_unused

The empty suspend/resume functions cause a build warning
when they are unused:

drivers/media/platform/qcom/camss/camss.c:1001:12: error: 'camss_runtime_resume' defined but not used [-Werror=unused-function]
drivers/media/platform/qcom/camss/camss.c:996:12: error: 'camss_runtime_suspend' defined but not used [-Werror=unused-function]

Mark them as __maybe_unused so the compiler can silently drop them.

Fixes: 02afa816 ("media: camss: Add basic runtime PM support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Todor Tomov <todor.tomov@linaro.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/platform/qcom/camss/camss.c

@@ -993,12 +993,12 @@ static const struct of_device_id camss_dt_match[] = {
 
 MODULE_DEVICE_TABLE(of, camss_dt_match);
 
-static int camss_runtime_suspend(struct device *dev)
+static int __maybe_unused camss_runtime_suspend(struct device *dev)
 {
 	return 0;
 }
 
-static int camss_runtime_resume(struct device *dev)
+static int __maybe_unused camss_runtime_resume(struct device *dev)
 {
 	return 0;
 }