ext4: correct comment references to ext4_ext_direct_IO()

Commit 914f82a3 "ext4: refactor direct IO code" deleted
ext4_ext_direct_IO(), but references to that function remain in
comments.  Update them to refer to ext4_direct_IO_write().
Signed-off-by: Eric Whitney <enwlinux@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Reviewed-by: Jan Kara <jack@suse.cz>

fs/ext4/inode.c

@@ -892,7 +892,7 @@ static int ext4_dio_get_block_unwritten_async(struct inode *inode,
 /*
  * Get block function for non-AIO DIO writes when we create unwritten extent if
  * blocks are not allocated yet. The extent will be converted to written
- * after IO is complete from ext4_ext_direct_IO() function.
+ * after IO is complete by ext4_direct_IO_write().
  */
 static int ext4_dio_get_block_unwritten_sync(struct inode *inode,
 		sector_t iblock, struct buffer_head *bh_result,	int create)
@@ -907,7 +907,7 @@ static int ext4_dio_get_block_unwritten_sync(struct inode *inode,
 
 	/*
 	 * Mark inode as having pending DIO writes to unwritten extents.
-	 * ext4_ext_direct_IO() checks this flag and converts extents to
+	 * ext4_direct_IO_write() checks this flag and converts extents to
 	 * written.
 	 */
 	if (!ret && buffer_unwritten(bh_result))