Exynos4210 based platforms have switched over to use generic
cpufreq driver for cpufreq functionality. So the Exynos
specific cpufreq support for these platforms can be removed.

Changes by Bartlomiej:
- dropped Exynos5250 support removal for now
- updated exynos-cpufreq.[c,h]

Cc: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>