[PATCH v2] ARM: sa1100: improve irq handling

[Dmitry Eremin-Solenikov]

Hello,

This patch series makes sa1100 platform use MULTI_IRQ_HANDLER and irq
domains to handle interrupts on StrongARM platform. Also virtual irq
numbers are changed to start from 1 rather than 0. It doesn't change
the way how Linux programs the hardware, only software interfaces are
changed.

Changes since v1:
- Start IRQs from 1, freeing IRQ 0
- Merge identical functions in the last patch
- Other minor changes.