iio: light: apds9960: correct ->last_busy count

Add missing pm_runtime_mark_last_busy to apds9960_set_power_state
function.

Unless pm_runtime_mark_last_busy is called the
pm_runtime_put_autosuspend may put the device into suspend before the
delay time requested.
Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/apds9960.c

@@ -453,6 +453,7 @@ static int apds9960_set_power_state(struct apds9960_data *data, bool on)
 			usleep_range(data->als_adc_int_us,
 				     APDS9960_MAX_INT_TIME_IN_US);
 	} else {
+		pm_runtime_mark_last_busy(dev);
 		ret = pm_runtime_put_autosuspend(dev);
 	}