ARM: 5823/1: SA1100: h3100/h3600: add support for gpio-keys

Add support for "Power" and "Action" (joystick center) buttons -
the only buttons on iPaq h3100/h3600 connected to GPIOs
(other buttons are controlled by microcontroller)
Also remove setting PWER for wakeup on Power button press -
gpio-keys driver will handle it.

Signed-off-by: Dmitry Artamonow <mad_soft@inbox.ru>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>