power: Use monotonic time for interaction boost

Using the wall clock will cause boosts to be disabled
when/if the clock is adjusted backward.

Bug: 29191415
Bug: 29208304
Change-Id: I8af5f40b46d996ce7bccb8324fc186e2f3a5b267
(cherry picked from commit 2bf13f822cf39123ee0e97e40caf1288ba4f457a)
2 files changed