sched: Update cur_freq in the cpufreq policy notifier callback

At boot, the cpufreq framework sends transition notifiers before
sending out the policy notifier. Since the scheduler relies on the
policy notifier to build up the frequency domain masks, when the
initial set of transition notifiers are sent, the scheduler has no
frequency domains. As a result the scheduler fails to update the
cur_freq information. Update cur_freq as part of the policy notifier
so that the scheduler always has the current frequency information.

Change-Id: I7bd2958dfeb064dd20b9ccebafd372436484e5d6
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>