Serial::end hang (#5047)

workaround for #5043. There is a timing issue with HardwareSerial::end. I'm not sure what is hung, but it should be possible to see this in jtag, as it does cause a reboot if you let it. The delay needs to be before you detach the device!?

cores/esp32/HardwareSerial.cpp

@@ -117,6 +117,7 @@ void HardwareSerial::end()
     if(uartGetDebug() == _uart_nr) {
         uartSetDebug(0);
     }
+    delay(10);
     log_v("pins %d %d",_tx_pin, _rx_pin);
     uartEnd(_uart, _tx_pin, _rx_pin);
     _uart = 0;