ARM: EXYNOS: remove useless code to save/restore L2

Following the merge of CPU PM notifiers and L2 resume code, this patch
removes useless code to save and restore L2 registers.

This is now automatically covered by suspend calls which integrated
CPU PM notifiers and new sleep code that allows to resume L2 before MMU
is turned on.

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>