dt-bindings: arm: keystone: Convert ti,sci to json schema

Convert the ti,sci to json schema for better checks and documentation.

NOTE: This change does introduce a stricter naming convention for
TI-SCI controller nodes.

Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Tero Kristo <kristo@kernel.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20210426155457.21221-5-nm@ti.com


Signed-off-by: Rob Herring <robh@kernel.org>