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: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>