ARM: dts: stm32: osd32: move pwr_regulators to common

According to the OSD32MP1 Power System overview[1] pwr_regulators;
vdd-supply and vdd_3v3_usbfs-supply are hard-wired internally in
the SIP module to vdd and ldo4.

[1]:
https://octavosystems.com/app_notes/osd32mp1-power-system-overview/#connections



Signed-off-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>