uid_cputime: Extends the cputime functionality to report power per uid

/proc/uid_cputime/show_uid_stats shows a third field power for each of
the uids. It represents the power in the units (uAusec)

Bug: 21498425
Change-Id: I52fdc5e59647e9dc97561a26d56f462a2689ba9c
Signed-off-by: Ruchi Kandoi <kandoiruchi@google.com>
Git-commit: b8d3311e8d41c9109f9a4ba3c4d0f7e594539c68
Git-repo: https://android.googlesource.com/kernel/msm/


Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>