the reserved bootloader size is set in the NVM user configuration
and allows to know the application start address (e.g. after the
bootloader)
Change-Id: I9dda27d6401caabb4a6470aa3fe9691f63097136
uses the USB CDC ACM example code as template to create a USB DFU
description according to USB DFU specification version 1.1
USB DFU stack is under LGPLv2.1 or later license
Change-Id: I7bd6cb46b734ffe8a51f2de7083b4f9e76d385e6