input: serio: ams-delta: toggle keyboard power over GPIO

Don't use Amstrad Delta custom I/O functions once GPIO interface is
available for the underlying hardware.

While requesting and initializing GPIO pins used, also take care of one
extra pin KEYBRD_DATAOUT which, even if not used by the driver, belongs
to the device and affects its functioning.

Once done, move the driver initialization back to the device_initcall
level, reverting the temporary chane introduced with patch 1/7 "ARM:
OMAP1: ams-delta: register latch dependent devices later".  That change
is no longer required once the driver takes care of registering used
GPIO pins, and it's better to initialize the device before others using
the latch2 based GPIO pins, otherwise a garbage is reported on boot,
perhaps due to random data already captured by the FIQ handler while the
keyboard related latch bits are written with random values during
initialization of those other latch2 dependent devices.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Acked-by: Dmitry Torokhov <dtor@mail.ru>
[tony@atomide.com: renamed _gpios to ams_delta_gpios]
Signed-off-by: Tony Lindgren <tony@atomide.com>