STM32 ACM Linux driver added

• The driver in the kernel is added as follows:

    x Symbol: USB_ACM [=y]                                                    x
    x Type  : tristate                                                        x
    x Prompt: USB Modem (CDC ACM) support                                     x
    x   Defined at drivers/usb/class/Kconfig:7                                x
    x   Depends on: USB_SUPPORT [=y] && USB [=y]                              x
    x   Location:                                                             x
    x     -> Device Drivers                                                   x
    x       -> USB support (USB_SUPPORT [=y])                                 x
    x   Selected by: USB_VL600 [=n] && NETDEVICES [=y] && USB [=y] && NET [=y 

• After adding, the microcontroller can become a ttyUSB device