[media] ad5820: use __maybe_unused for PM functions

The new ad5820 driver uses #ifdef to hide the suspend/resume functions,
but gets it wrong when CONFIG_PM_SLEEP is disabled:

drivers/media/i2c/ad5820.c:286:12: error: 'ad5820_resume' defined but not used [-Werror=unused-function]
drivers/media/i2c/ad5820.c:274:12: error: 'ad5820_suspend' defined but not used [-Werror=unused-function]

This replaces the #ifdef with a __maybe_unused annotation that is
simpler and harder to get wrong, avoiding the warning.

Fixes: bee3d511 ("[media] ad5820: Add driver for auto-focus coil")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/i2c/ad5820.c

@@ -269,9 +269,7 @@ static const struct v4l2_subdev_internal_ops ad5820_internal_ops = {
 /*
  * I2C driver
  */
-#ifdef CONFIG_PM
-
-static int ad5820_suspend(struct device *dev)
+static int __maybe_unused ad5820_suspend(struct device *dev)
 {
 	struct i2c_client *client = container_of(dev, struct i2c_client, dev);
 	struct v4l2_subdev *subdev = i2c_get_clientdata(client);
@@ -283,7 +281,7 @@ static int ad5820_suspend(struct device *dev)
 	return ad5820_power_off(coil, false);
 }
 
-static int ad5820_resume(struct device *dev)
+static int __maybe_unused ad5820_resume(struct device *dev)
 {
 	struct i2c_client *client = container_of(dev, struct i2c_client, dev);
 	struct v4l2_subdev *subdev = i2c_get_clientdata(client);
@@ -295,13 +293,6 @@ static int ad5820_resume(struct device *dev)
 	return ad5820_power_on(coil, true);
 }
 
-#else
-
-#define ad5820_suspend	NULL
-#define ad5820_resume	NULL
-
-#endif /* CONFIG_PM */
-
 static int ad5820_probe(struct i2c_client *client,
 			const struct i2c_device_id *devid)
 {