USB device stack

Dependents:   blinky_max32630fthr FTHR_USB_serial FTHR_OLED HSP_RPC_GUI_3_0_1 ... more

Fork of USBDevice by mbed official

Fix USBSerial compilation

The USBSerial device does not compile because it casts a function pointer to an int32. This change fixes it.

USBDevice with compilation error in USBSerial fixed.