drbd: Fixed a stupid copy and paste error

This caused rs_planed to be not in sync with the content of the fifo.
That in turn could cause that the resync comes to a complete halt.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_worker.c

@@ -421,7 +421,7 @@ static void fifo_set(struct fifo_buffer *fb, int value)
 	int i;
 
 	for (i = 0; i < fb->size; i++)
-		fb->values[i] += value;
+		fb->values[i] = value;
 }
 
 static int fifo_push(struct fifo_buffer *fb, int value)