MIPS: Alchemy: update core interrupt code.

This patch attempts to modernize core Alchemy interrupt handling code.

- add irq_chips for irq controllers instead of irq type,
- add a set_type() hook to change irq trigger type during runtime,
- add a set_wake() hook to control GPIO0..7 based wakeup,
- use linux' IRQF_TRIGGER_ constants instead of homebrew ones,
- enable GENERIC_HARDIRQS_NO__DO_IRQ.
- simplify plat_irq_dispatch
- merge au1xxx_irqmap into irq.c file, the only place where its
  contents are referenced.
- board_init_irq() is now mandatory for every board; use it to register
  the remaining (gpio-based) interrupt sources; update all boards
  accordingly.

Run-tested on Db1200 and other Au1200 based platforms.

Signed-off-by: Manuel Lauss <mano@roarinelk.homelinux.net>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

 delete mode 100644 arch/mips/alchemy/common/au1xxx_irqmap.c