mach-exynos: cpufreq: Show list of available frequencies

This patch enables 'scaling_available_frequencies' attribute
showing list of available frequencies.

Change-Id: I9b6ad786ffaaba8ad6fe5aa9045fd793c095b5ae
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_kernel_samsung_smdk4412 into cm-11.0