ANDROID: cpufreq_stat: add per task/uid/freq stats

Adds per process nodes in /proc/PID/time_in_state showing per
frequency times and adds a global /proc/uid_time_in_state
showing per frequency per uid times.

Bug: 34133340
Bug: 38320164

Tests: boot sailfish and reading /proc/uid_time_in_state and
/proc/$$/time_in_state

Signed-off-by: Andres Oportus <andresoportus@google.com>
Change-Id: Ideb22b608b9a5e7bd2200a3a6df0f110b635f96a