dm: rename request variables to bios

Use 'bio' in the name of variables and functions that deal with
bios rather than 'request' to avoid confusion with the normal
block layer use of 'request'.

No functional changes.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 5a578d8..9a01d1e 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -1151,7 +1151,7 @@
 
 	INIT_WORK(&rs->md.event_work, do_table_event);
 	ti->private = rs;
-	ti->num_flush_requests = 1;
+	ti->num_flush_bios = 1;
 
 	mutex_lock(&rs->md.reconfig_mutex);
 	ret = md_run(&rs->md);