iio:adc:at91-adc: Switch from CONFIG_PM_SLEEP guards to pm_sleep_ptr() etc

Letting the compiler remove these functions when the kernel is built
without CONFIG_PM_SLEEP support is simpler and less error prone than the
use of ifdef based config guards.

Removing instances of this approach from IIO also stops them being
copied into new drivers.
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20220130193147.279148-11-jic23@kernel.org

drivers/iio/adc/at91_adc.c

@@ -1234,7 +1234,6 @@ static int at91_adc_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM_SLEEP
 static int at91_adc_suspend(struct device *dev)
 {
 	struct iio_dev *idev = dev_get_drvdata(dev);
@@ -1256,9 +1255,9 @@ static int at91_adc_resume(struct device *dev)
 
 	return 0;
 }
-#endif
 
-static SIMPLE_DEV_PM_OPS(at91_adc_pm_ops, at91_adc_suspend, at91_adc_resume);
+static DEFINE_SIMPLE_DEV_PM_OPS(at91_adc_pm_ops, at91_adc_suspend,
+				at91_adc_resume);
 
 static const struct at91_adc_trigger at91sam9260_triggers[] = {
 	{ .name = "timer-counter-0", .value = 0x1 },
@@ -1386,7 +1385,7 @@ static struct platform_driver at91_adc_driver = {
 	.driver = {
 		   .name = DRIVER_NAME,
 		   .of_match_table = at91_adc_dt_ids,
-		   .pm = &at91_adc_pm_ops,
+		   .pm = pm_sleep_ptr(&at91_adc_pm_ops),
 	},
 };