use SERIAL_PORT_MONITOR Insteed of Serial5

cores/validation/validation_usb_host/build_as6/test.cppproj

cores/validation/validation_usb_host/test_USB_desc.cpp

.../validation_usb_host/test_usb_host_KeyboardController.cpp

...ion/validation_usb_host/test_usb_host_MouseController.cpp

cores/validation/validation_usb_host/test_usb_host_adk.cpp

variants/arduino_zero/variant.h