ARM: 8231/1: sa1100: introduce irqdomains support

Use irqdomains to manage both system and GPIO interrupts on SA1100 SoC
family. This opens path to further cleanup and unification in sa1100 IRQ
drivers.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>