nfsd: Cleanup - Let nfsd4_lookup_stateid() take a cstate argument

The cstate already holds information about the session, and hence
the client id, so it makes more sense to pass that information
rather than the current practice of passing a 'minor version' number.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>