Move firmware to a subdirectory

firmware/teensy3/touch.c

firmware/teensy3/usb_desc.c

firmware/teensy3/usb_desc.h

firmware/teensy3/usb_dev.c

firmware/teensy3/usb_dev.h

firmware/teensy3/usb_flightsim.cpp

firmware/teensy3/usb_flightsim.h

firmware/teensy3/usb_inst.cpp

firmware/teensy3/usb_joystick.c

firmware/teensy3/usb_joystick.h

firmware/teensy3/usb_keyboard.c

firmware/teensy3/usb_keyboard.h

firmware/teensy3/usb_mem.c

firmware/teensy3/usb_mem.h

firmware/teensy3/usb_midi.c

firmware/teensy3/usb_midi.h

firmware/teensy3/usb_mouse.c

firmware/teensy3/usb_mouse.h

firmware/teensy3/usb_names.h

firmware/teensy3/usb_rawhid.c