cpufreq: interactive: Use correct kobj when creating sysfs

cpufreq_global_kobject is no longer initialized during cpufreq_core_init.
Fix sysfs creation by properly requesting the kobject based on
have_governor_per_policy().

Change-Id: I5f9cff68043dad8822952bd43227d948a934a1c7
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>