isp_wrapper: few minor improvements & allow repeated start / stop#2

avolmat-st wants to merge 3 commits intostm32-hotspot:mainstm32-hotspot/zephyr-stm32-mw-isp:mainfrom

avolmat-st:pr-allow-start-stopavolmat-st/zephyr-stm32-mw-isp:pr-allow-start-stopCopy head branch name to clipboard