Merge pull request #7158 from OTAkeys/pr/stmclk_f4

boards/f4vi1/include/periph_conf.h

boards/msbiot/include/periph_conf.h

boards/nucleo-f401/include/periph_conf.h

boards/nucleo-f410/include/periph_conf.h

boards/nucleo-f411/include/periph_conf.h

boards/nucleo-f446/include/periph_conf.h

boards/nucleo144-f413/include/periph_conf.h

boards/nucleo144-f429/include/periph_conf.h

boards/nucleo144-f446/include/periph_conf.h

boards/stm32f4discovery/include/periph_conf.h

cpu/stm32f4/cpu.c

cpu/stm32f4/include/vendor/stm32f401xe.h

cpu/stm32f4/include/vendor/stm32f407xx.h

cpu/stm32f4/include/vendor/stm32f410rx.h

cpu/stm32f4/include/vendor/stm32f411xe.h

cpu/stm32f4/include/vendor/stm32f415xx.h

cpu/stm32f4/include/vendor/stm32f429xx.h

cpu/stm32f4/include/vendor/stm32f446xx.h

cpu/stm32f4/stmclk.c