UBIFS: Fix possible memory leak in ubifs_readdir()

If ubifs_tnc_next_ent() returns something else than -ENOENT
we leak file->private_data.

CRs-Fixed: 975289
Change-Id: I0194a58b45a8d4f103c67e48aafcdfa655dba92e
Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: David Gstir <david@sigma-star.at>
Git-commit: aeeb14f763917ccf639a602cfbeee6957fd944a2
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Nikhilesh Reddy <reddyn@codeaurora.org>