[PATCH] v9fs_vfs_mkdir(): fix a double free

Fix a double free of "dfid" introduced by commit
da977b2c

 and spotted by the Coverity
checker.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>