feat(st-clock): add function to restore generic timer rate

Add a function to restore the CPU generic timer rate from STGEN content.
After wake-up from LPLV-Stop2, STGEN content is not lost, but generic timer
has been reset.

Signed-off-by: Pascal Paillet <p.paillet@st.com>
Change-Id: I6f91dbd051f76383e9ff1d6bb86225d373dbf33a
2 files changed