AudioTrack: Fix Java offload blocking in AudioTrack::write

With Java offload support, both the AudioTrack::write() and the
AudioTrackThread obtainBuffer/waitStreamEndDone can be blocked
on the AudioTrackShared Proxy futex.

Prior to the Java offload support, AudioTrack::write() was not
called simultaneous to the AudioTrackThread
obtainBuffer/waitStreamEndDone, thus only one thread was
blocked on the futex.

Solution: Change the FUTEX_WAKE to wake more than one thread

Test: invoke android.media.cts.AudioTrackOffloadTest#testMP3AudioTrackOffload
repeatly, check if the case may blocked in AudioTrack::write (syscall)
Bug: 209612569
Change-Id: I40d531863486f66e65c2bfe7d8e00156c804232d