ARM: EXYNOS: save L2 settings during bootup

This patch adds code to save L2 register configuration at boot, and
later used to resume L2 before MMU is enabled in suspend and cpuidle
resume paths.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>