UBI: fix s/then/than/ typos

Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index f64ddab..ee7b1d8 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -350,7 +350,7 @@
  * @max: highest possible erase counter
  *
  * This function looks for a wear leveling entry with erase counter closest to
- * @max and less then @max.
+ * @max and less than @max.
  */
 static struct ubi_wl_entry *find_wl_entry(struct rb_root *root, int max)
 {