Migrate BatteryStats audio calls to oneway

The batterystats binder interfaces used by audioserver are currently
synchronous, which causes layering violations leading to threadpool
starvation in system server.

Migrate the calls used by audioserver in particular to oneway. These
calls are already void returning, and are logically async.

Fixes: 330359963
Test: dumpsys batterystats contains audio info
Change-Id: I271eb5e8cf709e0e7b74ed767c5e232ba0e548b7