ARM: 7389/2: plat-versatile: modernize FPGA IRQ controller

ARM: 7389/2: plat-versatile: modernize FPGA IRQ controller

This does two things to the FPGA IRQ controller in the versatile
family:

- Convert to MULTI_IRQ_HANDLER so we can drop the entry macro
  from the Integrator. The C IRQ handler was inspired from
  arch/arm/common/vic.c, recent bug discovered in this handler was
  accounted for.
- Convert to using IRQ domains so we can get rid of the NO_IRQ
  mess and proceed with device tree and such stuff.

As part of the exercise, bump all the low IRQ numbers on the
Integrator PIC to start from 1 rather than 0, since IRQ 0 is
now NO_IRQ. The Linux IRQ numbers are thus entirely decoupled
from the hardware IRQ numbers in this controller.

I was unable to split this patch. The main reason is the half-done
conversion to device tree in Versatile.

Tested on Integrator/AP and Integrator/CP.

Cc: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>