ubifs: Fix spelling mistakes

Fix some spelling mistakes in comments:
withoug  ==> without
numer  ==> number
aswell  ==> as well
referes  ==> refers
childs  ==> children
unnecesarry  ==> unnecessary

Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Reviewed-by: Alexander Dahl <ada@thorsis.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
diff --git a/fs/ubifs/tnc_commit.c b/fs/ubifs/tnc_commit.c
index 234be1c..58c92c9 100644
--- a/fs/ubifs/tnc_commit.c
+++ b/fs/ubifs/tnc_commit.c
@@ -930,7 +930,7 @@ static int write_index(struct ubifs_info *c)
 		 * flag cleared before %COW_ZNODE. Specifically, it matters in
 		 * the 'dirty_cow_znode()' function. This is the reason for the
 		 * first barrier. Also, we want the bit changes to be seen to
-		 * other threads ASAP, to avoid unnecesarry copying, which is
+		 * other threads ASAP, to avoid unnecessary copying, which is
 		 * the reason for the second barrier.
 		 */
 		clear_bit(DIRTY_ZNODE, &znode->flags);