ext4: ext4_ext_migrate should use NULL not 0

ext4_ext_migrate() calls ext4_new_inode() and passes 0 instead of a pointer
to a struct qstr.  This patch uses NULL, to make it obvious to the caller
that this was a pointer.
Signed-off-by: NEric Paris <eparis@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/migrate.c

@@ -496,7 +496,7 @@ int ext4_ext_migrate(struct inode *inode)
 	goal = (((inode->i_ino - 1) / EXT4_INODES_PER_GROUP(inode->i_sb)) *
 		EXT4_INODES_PER_GROUP(inode->i_sb)) + 1;
 	tmp_inode = ext4_new_inode(handle, inode->i_sb->s_root->d_inode,
-				   S_IFREG, 0, goal);
+				   S_IFREG, NULL, goal);
 	if (IS_ERR(tmp_inode)) {
 		retval = -ENOMEM;
 		ext4_journal_stop(handle);