Fix frequency pinning on crosperf.

Crosperf was pinning frequency to maximum based on cpu0
information. This does not work as intended for arm
Big-Little cores. Instead do it for each cpu based on its
own information.

BUG=chromium:680742
TEST=Tested on elm, kevin, falco, samus, peach_pit and veyron_jaq.

Change-Id: I77fc76d8f1e94563fe12b3555bf08511fdbfdc32
Reviewed-on: https://chromium-review.googlesource.com/428186


Commit-Ready: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Luis Lozano <llozano@chromium.org>