iio: imx8qxp-adc: mark PM functions as __maybe_unused

Without CONFIG_PM_SLEEP, the runtime suspend/resume functions
are unused, producing a warning:

drivers/iio/adc/imx8qxp-adc.c:433:12: error: 'imx8qxp_adc_runtime_resume' defined but not used [-Werror=unused-function]
  433 | static int imx8qxp_adc_runtime_resume(struct device *dev)
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/iio/adc/imx8qxp-adc.c:419:12: error: 'imx8qxp_adc_runtime_suspend' defined but not used [-Werror=unused-function]
  419 | static int imx8qxp_adc_runtime_suspend(struct device *dev)
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~

Mark them as __maybe_unused to shut up the compiler.

Fixes: 1e23dcaa ("iio: imx8qxp-adc: Add driver support for NXP IMX8QXP ADC")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Cai Huoqing <caihuoqing@baidu.com>
Link: https://lore.kernel.org/r/20211013144338.2261316-1-arnd@kernel.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/imx8qxp-adc.c

@@ -416,7 +416,7 @@ static int imx8qxp_adc_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static int imx8qxp_adc_runtime_suspend(struct device *dev)
+static __maybe_unused int imx8qxp_adc_runtime_suspend(struct device *dev)
 {
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 	struct imx8qxp_adc *adc = iio_priv(indio_dev);
@@ -430,7 +430,7 @@ static int imx8qxp_adc_runtime_suspend(struct device *dev)
 	return 0;
 }
 
-static int imx8qxp_adc_runtime_resume(struct device *dev)
+static __maybe_unused int imx8qxp_adc_runtime_resume(struct device *dev)
 {
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 	struct imx8qxp_adc *adc = iio_priv(indio_dev);