When flashing STM32N6 in USB-DFU mode, as required when running test
automation using twister, it is first required to power-off/power-on the
board to set board ready for USB-DFU (thanks to specific BootROM
configuration).
Provide a script that performs this operation using STM32CubeProgrammer.
This scipt could be provided in twister map.yaml file on 'pre_script'
property of board entry.
Signed-off-by: Erwan Gouriou <erwan.gouriou@st.com>
