UBI: fix add_fastmap() to use the vid_hdr passed in argument

add_fastmap() is passed a ubi_vid_hdr pointer in argument, but is
referencing the global vidh pointer.
Even if this is correct from a functional point of view (vidh and vid_hdr
point to the same object), it is confusing.
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

drivers/mtd/ubi/attach.c

@@ -197,8 +197,8 @@ static int add_fastmap(struct ubi_attach_info *ai, int pnum,
 		return -ENOMEM;
 
 	aeb->pnum = pnum;
-	aeb->vol_id = be32_to_cpu(vidh->vol_id);
-	aeb->sqnum = be64_to_cpu(vidh->sqnum);
+	aeb->vol_id = be32_to_cpu(vid_hdr->vol_id);
+	aeb->sqnum = be64_to_cpu(vid_hdr->sqnum);
 	aeb->ec = ec;
 	list_add(&aeb->u.list, &ai->fastmap);