clock_control: Add stm32mp157c_dk2 board support Add support for stm32mp1x RCC with Zephyr clock_control driver Signed-off-by: Yaël Boutreux <yael.boutreux@st.com> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com> Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>