ARM: dts: keystone: Remove ti,keystone from soc node compatible

This is just a "simple-bus" node, there is no need for the extra
compatible "ti,keystone" which is unused and undocumented.

Signed-off-by: Andrew Davis <afd@ti.com>
Link: https://lore.kernel.org/r/20230515183515.509371-4-afd@ti.com


Signed-off-by: Nishanth Menon <nm@ti.com>