arm: dts: k3-am654: add vin-supply regulators for DDR

arm: dts: k3-am654: add vin-supply regulators for DDR

As of commit f98d812e5353 ("power: regulator: Add vin-supply for GPIO
and Fixed regulators") we must ensure the parent nodes of a regulator
are present in DT if they are described in the vin-supply property

For the am65x reference board the DRAM chips are fed by the 3v3 rail
which is fed by the main 12v rail. Add the bootph properties to these DT
nodes to prevent them from being pruned during the SPL build so we can
enable power to the DRAM chips

Signed-off-by: Bryan Brattlof <bb@ti.com>
Tested-by: Nishanth Menon <nm@ti.com>