btrfs: fix comment typo in btrfs_finish_ordered_io

Fix typo errors in comments of btrfs_finish_ordered_io.

Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

fs/btrfs/inode.c

@@ -1969,8 +1969,8 @@ out:
 				      ordered_extent->len - 1, NULL, GFP_NOFS);
 
 	/*
-	 * This needs to be dont to make sure anybody waiting knows we are done
-	 * upating everything for this ordered extent.
+	 * This needs to be done to make sure anybody waiting knows we are done
+	 * updating everything for this ordered extent.
 	 */
 	btrfs_remove_ordered_extent(inode, ordered_extent);