sched: Update cur_freq for offline CPUs in notifier callback

cpufreq governor does not send frequency change notifications for
offline CPUs. This means that a hot removed CPU's cur_freq information
can get stale if there is a frequency change while that CPU is offline.
When the offline CPU is hotplugged back in, all subsequent load
calculations are based off the stale information until another frequency
change occurs and the corresponding set of notifications are sent out.
Avoid this incorrect load tracking by updating the cur_freq for all
CPUs in the same frequency domain.

Change-Id: Ie11ad9a64e7c9b115d01a7c065f22d386eb431d5
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>