NLM: Fix sparse warnings

 - fs/lockd/xdr4.c:140:27: warning: incorrect type in argument 2 (different
   explicit signedness)
 - fs/lockd/xdr4.c:141:27: warning: incorrect type in argument 2 (different
   explicit signedness)
 - fs/lockd/xdr4.c:432:28: warning: incorrect type in argument 2 (different
   explicit signedness)
 - fs/lockd/xdr4.c:433:28: warning: incorrect type in argument 2 (different
   explicit signedness)
 - fs/lockd/xdr4.c:587:20: warning: symbol 'nlm_version4' was not declared.
   Should it be static?

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>