blktrace: remove unused variable

index 5f74ef2..6c3533e 100644
@@ -1728,11 +1728,10 @@ static int handle_pfds_netclient(struct tracer *tp, int nevs, int force_read)
 {
 	struct stat sb;
 	int i, nentries = 0;
-	struct pdc_stats *sp;
 	struct pollfd *pfd = tp->pfds;
 	struct io_info *iop = tp->ios;
 
-	for (i = 0; i < ndevs; i++, pfd++, iop++, sp++) {
+	for (i = 0; i < ndevs; i++, pfd++, iop++) {
 		if (pfd->revents & POLLIN || force_read) {
 			if (fstat(iop->ifd, &sb) < 0) {
 				perror(iop->ifn);