Update f7's stage_1_boot

...cortexM7_stm32f7/stm32f756zg_nucleo/core/stage_1_boot.cpp

...M7_stm32f7/stm32f767zi_compute_unit/core/stage_1_boot.cpp

...cortexM7_stm32f7/stm32f767zi_nucleo/core/stage_1_boot.cpp

...texM7_stm32f7/stm32f769ni_discovery/core/stage_1_boot.cpp