ARM: EXYNOS: add interrupt definitions for EXYNOS5250

This patch adds the interrupt definitions for EXYNOS5250 at
<mach/irqs.h> file and it is needed for EXYNOS5250 SoC.
As a note, for single zImage of EXYNOS4 and EXYNOS5, prefix
of EXYNOS4_ and EXYNOS5_ has been added.

Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>