ram: stm32mp1: increase vdd2_ddr: buck2 for 32bits LPDDR

Need to increase the LPDDR2/LPDDR3 the voltage vdd2_ddr: buck2
form 1.2V to 1.25V for 32bits configuration.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Acked-by: Patrice Chotard <patrice.chotard@st.com>