ARM: EXYNOS: switch to using generic cpufreq driver for exynos5250

The new CPU clock type allows the use of generic CPUfreq driver.
Switch Exynos5250 to using generic cpufreq driver.

Cc: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
[b.zolnierkie: split Exynos5250 support from the original patch]
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@dowhile0.org>
Tested-by: Javier Martinez Canillas <javier@dowhile0.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>