Permissions for I/O scheduler settings
(project CyanogenMod/android_packages_apps_Settings)

Refs: http://review.cyanogenmod.com/#/c/23531/

Same as for JB: http://review.cyanogenmod.com/#/c/22128/

Change-Id: I49ab2cfc69c3fae0026639453716d1db30a61b2f