stm32mp1: board: Update the way vdd-supply is retrieved from DT

Due to kernel DT alignment, pwr-supply is renamed to vdd-supply
and is a subnode of pwr-regulators.

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