Input: pxa27x_keypad - remove unnecessary ARM includes

Remove some left-over ARM only includes in order to enable building on
ARM64. __raw_{read,write}l were getting implicitly included, so add
linux/io.h include.

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>