jffs2: reduce the breakage on recovery from halfway failed rename()

jffs2: reduce the breakage on recovery from halfway failed rename()

Orabug: 23331003

[ Upstream commit f93812846f31381d35c04c6c577d724254355e7f ]

d_instantiate(new_dentry, old_inode) is absolutely wrong thing to
do - it will oops if new_dentry used to be positive, for starters.
What we need is d_invalidate() the target and be done with that.

Cc: stable@vger.kernel.org # v3.18+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit c62aadae234ffad0901c20ac1a1aa4e13cce1c20)

Signed-off-by: Dan Duval <dan.duval@oracle.com>