ARM: exynos: move exynos4210-combiner to drivers/irqchip

Exynos boot is broken with commit 0529e315 (ARM: use common irqchip_init
for GIC init). This commit split the irqchip initialization into 2 calls
to of_irq_init. This does not work because of_irq_init requires interrupt
parents to be in the match list.

Rather than reverting exynos changes, make it do the proper thing by using
IRQCHIP_DECLARE. This requires moving the combiner code to drivers/irqchip.

Reported-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-samsung-soc@vger.kernel.org
Signed-off-by: Olof Johansson <olof@lixom.net>