exynos: update tzpc to make it common for exynos4 and exynos5

This requires that cpu_is_exynos4/5 should be made available before tzpc_init.
Hence this patch also makes necessary changes to have cpu_info in spl and
invokes arch_cpu_init before tzpc_init in low_level_init.S for smdk5250.

Signed-off-by: Inderpal Singh <inderpal.singh@linaro.org>
Acked-by: Chander Kashyap <chander.kashyap@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>