ARM: SAMSUNG: Move timer irq numbers to end of linux irq space

The timer irqs statically mapped from linux irq numbers 11 to 15 are
moved to the end of the statically mapped linux irq space. The GIC PPI
and SPI interrupts are relocated to start from 16 and 32 of the linux
irq space. This is a required to add device tree support for GIC and
Interrupt combiner for EXYNOS4.

A new macro 'IRQ_TIMER_BASE' specifies a platform specific base of the
linux virq number for the timer interrupts. For exynos4, this base is
set to end of the linux virq space.  For the other S5P platforms, the
existing base '11' is retained.

Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>