ARM: nspire: Drop unused includes

Several includes are not needed, so drop them. io.h was implicitly included
and is needed.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230803-dt-header-cleanups-for-soc-v2-10-d8de2cc88bff@kernel.org


Signed-off-by: Arnd Bergmann <arnd@arndb.de>