arm64: Explicitly include correct DT includes

Remove unused 'of*.h' header inclusions from the arm64 arch code to
allow for the eventual untangling of 'of_device.h and 'of_platform.h',
which currently include each other.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230714174021.4039807-1-robh@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>