nfs: remove unnecessary check for NULL inode->i_flock from nfs_delegation_claim_locks

The second check was added in commit 65b62a29 but it will never be true.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>