UBI: Fastmap: Notify user in case of an ubi_update_fastmap() failure

If ubi_update_fastmap() fails notify the user.
This is not a hard error as ubi_update_fastmap() makes sure that upon failure
the current on-flash fastmap will no be used upon next UBI attach.
Signed-off-by: Richard Weinberger <richard@nod.at>

drivers/mtd/ubi/wl.c

@@ -654,7 +654,11 @@ int ubi_wl_get_peb(struct ubi_device *ubi)
 	 * refill the WL pool synchronous. */
 	if (pool->used == pool->size || wl_pool->used == wl_pool->size) {
 		spin_unlock(&ubi->wl_lock);
-		ubi_update_fastmap(ubi);
+		ret = ubi_update_fastmap(ubi);
+		if (ret) {
+			ubi_msg(ubi, "Unable to write a new fastmap: %i", ret);
+			return -ENOSPC;
+		}
 		spin_lock(&ubi->wl_lock);
 	}