NFS: Remove an unneeded check in decode_compound_header_arg()

Clean up:  The header tag length is unsigned, so checking that it is less
than zero is unnecessary.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/callback_xdr.c

@@ -139,7 +139,7 @@ static __be32 decode_compound_hdr_arg(struct xdr_stream *xdr, struct cb_compound
 	if (unlikely(status != 0))
 		return status;
 	/* We do not like overly long tags! */
-	if (hdr->taglen > CB_OP_TAGLEN_MAXSZ-12 || hdr->taglen < 0) {
+	if (hdr->taglen > CB_OP_TAGLEN_MAXSZ - 12) {
 		printk("NFSv4 CALLBACK %s: client sent tag of length %u\n",
 				__FUNCTION__, hdr->taglen);
 		return htonl(NFS4ERR_RESOURCE);