mach-stm32: Factorize MPU's region config for STM32 SoCs

MPU's region setup can be factorized between STM32F4/F7/H7 SoCs family
and used a common MPU's region config.

Only one exception for STM32H7 which doesn't have device area
located at 0xA000 0000.

For STM32F4, configure_clocks() need to be moved from arch_cpu_init()
to board_early_init_f().

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Vikas Manocha <vikas.manocha@st.com>