stm32mp1: ram: add support for LPDDR2/LPDDR3

Manage power supply configuration for board using stpmic1
with LPDDR2 or with LPDDR3:
+ VDD_DDR1 = 1.8V with BUCK3 (bypass if possible)
+ VDD_DDR2 = 1.2V with BUCK2

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
4 files changed