Comment fix: Fix the option associated with iperf_test.bind_port.

No functional change.

src/iperf.h

@@ -172,7 +172,7 @@ struct iperf_test
     signed char state;
     char     *server_hostname;                  /* -c option */
     char     *bind_address;                     /* -B option */
-    int       bind_port;                        /* -e option */
+    int       bind_port;                        /* --cport option */
     int       server_port;
     int       omit;                             /* duration of omit period (-O flag) */
     int       duration;                         /* total duration of test (-t flag) */