docs(iperf): Update documentation with console interface details

Closes espressif#12039

examples/wifi/iperf/README.md

@@ -16,33 +16,34 @@ This example implements the protocol used by the common performance measurement
 Performance can be measured between two ESP32s running this example, or between a single ESP32 and a computer running the iPerf tool
 
 Demo steps to test station TCP Tx performance:
+1. Configure in `menuconfig` which serial output you are using. Execute `idf.py menuconfig` and go to `Component config/ESP System Settings/Channel for console output`, then select the appropiate interface. By default the UART0 interface is used, this means that for example in the ESP32-S3-DevKitC-1 or ESP32-C6-DevKitC-1 you should connect to the micro-usb connector labeled as UART and not to the one labeled as USB. To use the one labeled as USB you should change the aforementioned setting to `USB Serial/JTAG Controller`.
 
-1. Build the iperf example with sdkconfig.defaults, which contains performance test specific configurations
+2. Build the iperf example with sdkconfig.defaults, which contains performance test specific configurations
 
-2. Run the demo as station mode and join the target AP
+3. Run the demo as station mode and join the target AP
    sta ssid password
 
-3. Run iperf as server on AP side
+4. Run iperf as server on AP side
    iperf -s -i 3
 
-4. Run iperf as client on ESP32 side
+5. Run iperf as client on ESP32 side
    iperf -c 192.168.10.42 -i 3 -t 60
 
 The console output, which is printed by station TCP RX throughput test, looks like:
 
->esp32> sta aptest
+>iperf> sta aptest
 >
 >I (5325) iperf: sta connecting to 'aptest'
 >
->esp32> I (6017) event: ip: 192.168.10.248, mask: 255.255.255.0, gw: 192.168.10.1
+>iperf> I (6017) event: ip: 192.168.10.248, mask: 255.255.255.0, gw: 192.168.10.1
 >
->esp32> iperf -s -i 3 -t 1000
+>iperf> iperf -s -i 3 -t 1000
 >
 >I (14958) iperf: mode=tcp-server sip=192.168.10.248:5001, dip=0.0.0.0:5001, interval=3, time=1000
 >
 >Interval Bandwidth
 >
->esp32> accept: 192.168.10.42,62958
+>iperf> accept: 192.168.10.42,62958
 >
 >0-   3 sec       8.43 Mbits/sec
 >