rt2x00: Fix queue index handling

When Q_INDEX is increased, the queue->length should be increased,
only when Q_INDEX_DONE is increased should queue_length be descreased.

Signed-off-by: Ivo van Doorn <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

drivers/net/wireless/rt2x00/rt2x00queue.c

···
 	if (queue->index[index] >= queue->limit)
 		queue->index[index] = 0;
 
-	queue->length--;
-	queue->count += (index == Q_INDEX_DONE);
+	if (index == Q_INDEX) {
+		queue->length++;
+	} else if (index == Q_INDEX_DONE) {
+		queue->length--;
+		queue->count ++;
+	}
 
 	spin_unlock(&queue->lock);
 }