cpufreq: interactive: fix race on cpufreq TRANSITION notifier

The cpufreq TRANSTION notifier callback does not check the
governor_enabled state on affected CPUS, which will case
kernel panic in update_load because the policy object maybe
NULL or invalid when governor_enabled is false.

Signed-off-by: Lianwei Wang <a22439@motorola.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>