ARM: exynos: exynos-cpufreq platform device isn't supported anymore

The driver is removed long back and we don't support this device
anymore. Stop adding it.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>