include: drivers: clock_control stm32 bus clock index can exceed 256

For some stm32 devices, especially the stm32H7RS serie,
the RCC register map is larger that 256 (example  AHB1 is 0x138).
The mask is extended to 0x1ff in the .bus of the clock info structure,
using the GENMASK macro from STM32_CLOCK_DIV_SHIFT

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