ARM: EXYNOS: Remove legacy timer initialization code

This patch removes legacy timer initialization code that was used to
set up system timers when booting with ATAGS, which is not supported
on Exynos any more.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>