md: remove 'go_faster' option from ->sync_request()

This option is not well justified and testing suggests that
it hardly ever makes any difference.

The comment suggests there might be a need to wait for non-resync
activity indicated by ->nr_waiting, however raise_barrier()
already waits for all of that.

So just remove it to simplify reasoning about speed limiting.

This allows us to remove a 'FIXME' comment from raid5.c as that
never used the flag.

Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 4efa501..9157a29 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -2480,7 +2480,7 @@
  * that can be installed to exclude normal IO requests.
  */
 
-static sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int *skipped, int go_faster)
+static sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int *skipped)
 {
 	struct r1conf *conf = mddev->private;
 	struct r1bio *r1_bio;
@@ -2533,13 +2533,6 @@
 		*skipped = 1;
 		return sync_blocks;
 	}
-	/*
-	 * If there is non-resync activity waiting for a turn,
-	 * and resync is going fast enough,
-	 * then let it though before starting on this new sync request.
-	 */
-	if (!go_faster && conf->nr_waiting)
-		msleep_interruptible(1000);
 
 	bitmap_cond_end_sync(mddev->bitmap, sector_nr);
 	r1_bio = mempool_alloc(conf->r1buf_pool, GFP_NOIO);