boards: define flash partitions for nucleo_h743zi
boards: define flash partitions for nucleo_h743zi

Defines partitions that can be used by mcuboot on nucleo_h743zi board.
Please note that mcuboot is not yet supported on stm32 h7 family as the
write-block-size is greater than 8.

Signed-off-by: Nicolas VINCENT <bf1fab8e8ae5f19954e27cd4beab79cce48f8e9f@vossloh.com>

galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr