ubifs: ubifs_add_orphan: Fix a memory leak bug

Memory leak occurs when files with extended attributes are added to
orphan list.

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Fixes: 988bec41 ("ubifs: orphan: Handle xattrs like files")
Signed-off-by: Richard Weinberger <richard@nod.at>