irqchip: atmel-aic: Add irq fixup infrastructure

irqchip: atmel-aic: Add irq fixup infrastructure

Add irq fixup infrastructure to handle IP blocks connected to shared irqs
that are left in an unknown state when booting the kernel.

In this case the IP block which has not masked its interrupt and has no
driver loaded (either because it is not compiled or because it is not
loaded yet) might generate spurious interrupts when another IP block
request the shared irq.

A good example of this case is the RTC block on which register configs are
kept even after a shutdown (if a proper VDDcore is supplied), and thus
might generate spurious interrupts when the platform is switched on.

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Link: https://lkml.kernel.org/r/1405016741-2407-2-git-send-email-boris.brezillon@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>