stmhal: Get USB enumerating a CDC device.

stmhal/Makefile

stmhal/boards/PYBOARD4/stm32f4xx_hal_conf.h

stmhal/main.c

stmhal/pendsv.c

stmhal/pendsv.h

stmhal/stm32f4xx_it.c

stmhal/stm32f4xx_it.h

stmhal/usb.c

stmhal/usb.h

stmhal/usbd_cdc_interface.c

stmhal/usbd_cdc_interface.h

stmhal/usbd_conf.c

stmhal/usbd_conf.h

stmhal/usbd_desc.c

stmhal/usbd_desc.h

stmhal/usbdev/class/AUDIO/Inc/usbd_audio.h

stmhal/usbdev/class/AUDIO/Inc/usbd_audio_if_template.h

stmhal/usbdev/class/AUDIO/Src/usbd_audio.c

stmhal/usbdev/class/AUDIO/Src/usbd_audio_if_template.c

stmhal/usbdev/class/CustomHID/Inc/usbd_customhid.h