Some of Exynos has the Security management Unit(SMU).
This patch adds the function for controlling SMU.

In future, if exynos needs to control SMU, it can be implemented
in "config_smu" function, not "init" function.
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>