dm: bio_list macro renaming

Remove BIO_LIST and DEFINE_BIO_LIST macros that gain us nothing
since contents are initialised to NULL.

Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
index 719f871..bdd37f8 100644
--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -83,7 +83,7 @@
 	struct dm_delay_info *delayed, *next;
 	unsigned long next_expires = 0;
 	int start_timer = 0;
-	BIO_LIST(flush_bios);
+	struct bio_list flush_bios = { };
 
 	mutex_lock(&delayed_bios_lock);
 	list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {