Add time spent by uid per cpu frequency to batterystats.

Currently we have total user and system cpu time spent by the uid
in the batterystats. This change will add times spent by the uid
at each different cpu frequency to the batterystats dump which will
help in better understanding the battery usage.

Bug: 34133340
Test: manual
Change-Id: I567dc75875eb58543c0e71572d0b440e87dbb4b9