NFSD: Squash an annoying compiler warning

Clean up: Fix gcc empty-body warning when -Wextra is used.

../fs/nfsd/nfs4state.c:3898:3: warning: suggest braces around empty body in an ‘else’ statement [-Wempty-body]
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4state.c

@@ -3881,12 +3881,11 @@ nfsd4_setclientid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	unconf = find_unconfirmed_client_by_name(&clname, nn);
 	if (unconf)
 		unhash_client_locked(unconf);
+	/* We need to handle only case 1: probable callback update */
 	if (conf && same_verf(&conf->cl_verifier, &clverifier)) {
-		/* case 1: probable callback update */
 		copy_clid(new, conf);
 		gen_confirm(new, nn);
-	} else /* case 4 (new client) or cases 2, 3 (client reboot): */
-		;
+	}
 	new->cl_minorversion = 0;
 	gen_callback(new, setclid, rqstp);
 	add_to_unconfirmed(new);