sched: cpufreq: Use per_cpu_ptr instead of this_cpu_ptr when reporting load

We need cpufreq_update_util to report load for the CPU corresponding
to the rq that is passed in as an argument, rather than the CPU executing
cpufreq_update_util.

Change-Id: I8473f230d40928d5920c614760e96fef12745d5a
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>