UBIFS: few spelling fixes

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 5bb272c..76405c4 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -986,7 +986,7 @@
 		switch (token) {
 		/*
 		 * %Opt_fast_unmount and %Opt_norm_unmount options are ignored.
-		 * We accepte them in order to be backware-compatible. But this
+		 * We accept them in order to be backward-compatible. But this
 		 * should be removed at some point.
 		 */
 		case Opt_fast_unmount: