ARM: Exynos: move interrupt combiner controller driver to drivers/irqchip

The irqchip support for interrupt combiner controller is moved into
drivers/irqchip directory from arch/arm/mach-exynos/common.c file.

While at it, the use of soc_is_exynos4/5() macro in the combiner controller
driver (used to determine the number of combiners) is removed. Instead, a new
parameter is added to combiner_init function that allows non-dt platform code
to specify the number of combiners available.

Signed-off-by: Thomas Abraham <thomas.abraham at linaro.org>