When decrypting dirents in ->readdir, fscrypt_fname_disk_to_usr won't
change content of original encrypted dirent, we don't need to allocate
additional buffer for storing mirror of it, so get rid of it.
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>