Input: ams_delta_serio: use IRQ resource

The driver still obtains IRQ number from a hardcoded GPIO.  Use IRQ
resource instead.

For this to work on Amstrad Delta, add the IRQ resource to
ams-delta-serio platform device structure.  Obtain the IRQ number
assigned to "keybrd_clk" GPIO pin from FIQ initialization routine.

As a benefit, the driver no longer needs to include
<mach/board-ams-delta.h>.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>