UBIFS: various minor commentary fixes

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c
index eaf6d89..c1f3f99 100644
--- a/fs/ubifs/budget.c
+++ b/fs/ubifs/budget.c
@@ -741,7 +741,7 @@
  * ubifs_get_free_space - return amount of free space.
  * @c: UBIFS file-system description object
  *
- * This function calculates and retuns amount of free space to report to
+ * This function calculates and returns amount of free space to report to
  * user-space.
  */
 long long ubifs_get_free_space(struct ubifs_info *c)