bootph-all as phase tag was added to dt-schema
(dtschema/schemas/bootph.yaml) to describe various node usage during
boot phases with DT.

Describe the same for AM642-sk boot devices.
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/20230911172902.1057417-4-nm@ti.comSigned-off-by: Vignesh Raghavendra <vigneshr@ti.com>