tools/power turbostat: Repair Segmentation fault when using -i option

Fix regression caused by commit 8e180f3
(tools/power turbostat: add [-d MSR#][-D MSR#] options to print counter
deltas)

Signed-off-by: Len Brown <len.brown@intel.com>

tools/power/x86/turbostat/turbostat.c

@@ -1594,7 +1594,7 @@ void cmdline(int argc, char **argv)
 
 	progname = argv[0];
 
-	while ((opt = getopt(argc, argv, "+pPSvisc:sC:m:M:")) != -1) {
+	while ((opt = getopt(argc, argv, "+pPSvi:sc:sC:m:M:")) != -1) {
 		switch (opt) {
 		case 'p':
 			show_core_only++;