Always wait until wakeup time if it is set.

Early returning causes the buffer always being pretty full. That will
cause the timestamp latency higher than it could be.

Bug: 420871788
Test: atest AAudioTests
Test: OboeTester TEST OUTPUT, Latency test
Flag: EXEMPT bugfix
Change-Id: I3ed9fe38395e726407ab16164be4a4c6df0ed937