iio:accel:stk8312: 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.

Signed-off-by: Jonathan Cameron <[e-mail]>
Reviewed-by: Paul Cercueil <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/iio/accel/stk8312.c

···
 	return stk8312_set_mode(data, STK8312_MODE_STANDBY);
 }
 
-#ifdef CONFIG_PM_SLEEP
 static int stk8312_suspend(struct device *dev)
 {
 	struct stk8312_data *data;
···
 	return stk8312_set_mode(data, data->mode | STK8312_MODE_ACTIVE);
 }
 
-static SIMPLE_DEV_PM_OPS(stk8312_pm_ops, stk8312_suspend, stk8312_resume);
-
-#define STK8312_PM_OPS (&stk8312_pm_ops)
-#else
-#define STK8312_PM_OPS NULL
-#endif
+static DEFINE_SIMPLE_DEV_PM_OPS(stk8312_pm_ops, stk8312_suspend,
+				stk8312_resume);
 
 static const struct i2c_device_id stk8312_i2c_id[] = {
 	/* Deprecated in favour of lowercase form */
···
 static struct i2c_driver stk8312_driver = {
 	.driver = {
 		.name = STK8312_DRIVER_NAME,
-		.pm = STK8312_PM_OPS,
+		.pm = pm_sleep_ptr(&stk8312_pm_ops),
 	},
 	.probe =            stk8312_probe,
 	.remove =           stk8312_remove,