clk: stm32f7: add STM32F4 support

STM32F4 and STM32F7 RCC clock IP are very similar.
Same driver can be used to managed RCC clock for
these 2 SoCs.

Differences between STM32F4 and F7 will be managed using
different compatible string :
 _ overdrive clock is only supported by STM32F7
 _ different sys_pll_psc parameters can be used between STM32F4
   and STM32F7.

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