clk: exynos4: Export clocks used by exynos cpufreq drivers

This patch exports clocks used by Exynos cpufreq drivers to allow lookup
using device tree. (Support to cpufreq drivers will be added in further
patches.)

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>