ARM: keystone: Drop unused includes

Several includes are not needed, so drop them.

of_platform.h is not needed, but it implicitly includes platform_device.h
(for now) which is needed.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230717225610.3214029-1-robh@kernel.org


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