iio: xilinx-xadc: Fix typo

Fix a typo. 'at the a time' -> 'at a time'.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/xilinx-xadc-core.c

@@ -653,7 +653,7 @@ static int xadc_trigger_set_state(struct iio_trigger *trigger, bool state)
 	mutex_lock(&xadc->mutex);
 
 	if (state) {
-		/* Only one of the two triggers can be active at the a time. */
+		/* Only one of the two triggers can be active at a time. */
 		if (xadc->trigger != NULL) {
 			ret = -EBUSY;
 			goto err_out;