include: binding defines division factor for stm32 MCO prescaler

Depending on the stm32 serie the MCO1/2 prescaler is a value
set in the CFGR register to divide the MCO output clock.
Use the same model based on the RefMan for other stm32 series
than stm32C0/F4/F7/H5/H7, once the MCO is in the DTS.

Signed-off-by: Francois Ramu <francois.ramu@st.com>