cpufreq: interactive: Add cpuload trace events

With per-cluster timer implementation, only max load across CPUs in
cluster is traced in timer function. Add cpufreq_interactive_cpuload
trace to provide per-cpu load information.

Change-Id: Icea9f2574332a4bc472b14193e77d76100a896ed
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>