cpufreq: Add cpu utilization statistics to aid decisions made by userspace.

Understanding system load as seen by cpufreq can help userspace
algorithms make better decisions to improve system responsiveness.
One such example would be the MP decision algorithm which mines
various system info to make decisions on hotplugging in/out
the additional cores.

Change-Id: I277db7e1a7803a3822b61e7befa25131487cfe17
Signed-off-by: Anitha Anand <anithas@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>