Multi Core Timer node has interrupts routed to two different parents -
GIC and combiner.  This was modeled with a interrupt-map within a
subnode but can be expressed in an easier and more common way, directly
in the node itself.

Tested on Odroid U3 (Exynos4412).
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>