Use new powerHintAsync when available

Use the async version of powerHint when available.

Bug: 62377008
Test: Run systrace, confirm powerHints are async HIDL transactions
Change-Id: I3bb4022b78d380b054bf13008bb8b0d399bf1955
Merged-In: I3bb4022b78d380b054bf13008bb8b0d399bf1955
2 files changed