UBI: Fastmap: Add blank line after declarations

Another checkpatch complaint:
WARNING: Missing a blank line after declarations
Signed-off-by: NRichard Weinberger <richard@nod.at>

drivers/mtd/ubi/fastmap-wl.c

@@ -21,6 +21,7 @@
 static void update_fastmap_work_fn(struct work_struct *wrk)
 {
 	struct ubi_device *ubi = container_of(wrk, struct ubi_device, fm_work);
+
 	ubi_update_fastmap(ubi);
 	spin_lock(&ubi->wl_lock);
 	ubi->fm_work_scheduled = 0;