Add a stack to support the Universal Serial Bus Device Class
Specification for Device Firmware Upgrade (USB DFU v1.1).
This stack is based on the USB device stack (USBD).
Change-Id: I8a56411d184882b6a9e3617c6dfb859086b8f353
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>