The RCC handles three sub-system clocks: ck_mpuss, ck_axiss
and ck_mcuss.
This patch adds also some MUX system and several prescalers.
Signed-off-by: NGabriel Fernandez <gabriel.fernandez@st.com>
Signed-off-by: NMichael Turquette <mturquette@baylibre.com>