ARM: EXYNOS: Remove GIC save & restore function

This patch removes GIC save & restore functino in pm.c. Because when
enalbe CPU_PM feature, GIC driver execute save and restore function
in CPU_PM notifier.
So it is not needed to GIC save & restore function at pm.c file.

Signed-off-by: Jongpill Lee <boyko.lee@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>