UBIFS: Delete unnecessary checks before the function call "iput"

The iput() function tests whether its argument is NULL and then
returns immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

CRs-Fixed: 975289
Change-Id: I46adad6d364bed3ab053974cfe71a568d548307f
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
Git-commit: 54bcfdf19ec7c2f2788fa76426c91abdc4dab973
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


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