irqchip: Add bcm2836 interrupt controller for Raspberry Pi 2

This interrupt controller is the new root interrupt controller with
the timer, PMU events, and IPIs, and the bcm2835's interrupt
controller is chained off of it to handle the peripherals.

I wrote the interrupt chip support, while Andrea Merello wrote the IPI
code.

Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Cc: linux-rpi-kernel@lists.infradead.org
Cc: Lee Jones <lee@kernel.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1438902033-31477-5-git-send-email-eric@anholt.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>