feat(st-clock): assign clocks to the correct BL

Some clocks are only required in BL2, like boot devices clocks:
FMC, QSPI.
Some clocks are only used in BL32: Timers, devices that need special
care for independent reset.

Change-Id: Id4ba99afeea5095f419a86f7dc6423192c628d82
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
Signed-off-by: Yann Gautier <yann.gautier@st.com>