Coverity spotted a superfluous error check in nfs4_open_revalidate().  Remove
it.

Coverity: #cid 847

Test plan:
Code inspection; another pass through Coverity.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>