The STM32 line of microcontrollers comes with a bootloader in the ROM.
It provides the option to flash the device firmware in DFU mode (USB)
or via UART or SPI.
To enter the bootloader we have to jump to a specific address in memory,
but before reset the CPU to make sure the system is in a known state.
This enables us to use the usb_board_reset module on all STM32 platforms.
