refactor(st): update CPU and VDD voltage get

Use regulator framework to get CPU and VDD power supplies.

Change-Id: Ice745fb21ff10e71ef811e747165499c2e19253e
Signed-off-by: Pascal Paillet <p.paillet@st.com>
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
2 files changed