MD: change journal disk role to disk 0

Neil pointed out setting journal disk role to raid_disks will confuse
reshape if we support reshape eventually. Switching the role to 0 (we
should be fine as long as the value >=0) and skip sysfs file creation to
avoid error.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 807095f..874c843 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1652,7 +1652,7 @@
 			rdev->journal_tail = le64_to_cpu(sb->journal_tail);
 			if (mddev->recovery_cp == MaxSector)
 				set_bit(MD_JOURNAL_CLEAN, &mddev->flags);
-			rdev->raid_disk = mddev->raid_disks;
+			rdev->raid_disk = 0;
 			break;
 		default:
 			rdev->saved_raid_disk = role;