MIPS: Octeon: Improve interrupt handling.

The main change is to change most of the IRQs from handle_percpu_irq
to handle_fasteoi_irq.  This necessitates extracting all the .ack code
to common functions that are not exposed to the irq core.

The affinity code now acts more sanely, by doing round-robin
distribution instead of broadcasting.

Because of the change to handle_fasteoi_irq and affinity, some of the
IRQs had to be split into separate groups with their own struct
irq_chip to prevent undefined operations on specific IRQ lines.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1485/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>