MIPS: SGI-IP27: rework HUB interrupts

This commit rearranges the HUB interrupt code by using MIPS_IRQ_CPU
interrupt handling code and modern Linux IRQ framework features to get
rid of global arrays. It also adds support for irq affinity setting.

Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org