Provide basic clock control driver for STM32H7.
Bus clock activation is done through CM7 and CM4 common registers
so we don't have to care to the CPU Id before accessing.
Accesses are not protected for now. Only possible configuration
is system clock source set to HSE driven PLL.
Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
Erwan Gouriou