irqchip/tango: Add support for Sigma Designs SMP86xx/SMP87xx interrupt controller

This adds support for the secondary interrupt controller used in Sigma
Designs SMP86xx and SMP87xx chips.

Signed-off-by: Mans Rullgard <mans@mansr.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/1453313237-18570-2-git-send-email-mans@mansr.com


Signed-off-by: Jason Cooper <jason@lakedaemon.net>