ARM: EXYNOS: Remove legacy EINT initialization code

This patch removes legacy EINT initialization code that was used to
handle external interrupts when booting with ATAGS, which is not
supported 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>