graid: unbreak Promise RAID1 with 4+ providers

Fix a problem in graid implementation of Promise RAID1 created with 4+ disks.
Such an array generally works fine until reboot only due to a bug
in metadata writing code. Before the fix, next taste erronously created
RAID1E (kind of RAID10) instead of RAID1, hence graid used wrong offsets
for I/O operations.

The bug did not affect Promise RAID1 arrays with 2 or 3 disks only.

Reviewed by:	mav
MFC after:	3 days

sys/geom/raid/md_promise.c

@@ -1762,8 +1762,9 @@ g_raid_md_write_promise(struct g_raid_md_object *md, struct g_raid_volume *tvol,
 		meta->total_disks = vol->v_disks_count;
 		meta->stripe_shift = ffs(vol->v_strip_size / 1024);
 		meta->array_width = vol->v_disks_count;
-		if (vol->v_raid_level == G_RAID_VOLUME_RL_RAID1 ||
-		    vol->v_raid_level == G_RAID_VOLUME_RL_RAID1E)
+		if (vol->v_raid_level == G_RAID_VOLUME_RL_RAID1)
+			meta->array_width = 1;
+		else if (vol->v_raid_level == G_RAID_VOLUME_RL_RAID1E)
 			meta->array_width /= 2;
 		meta->array_number = vol->v_global_id;
 		meta->total_sectors = vol->v_mediasize / 512;