AAudio: Use volume ramp

AAudio should have a volume ramp when stream starts.
Without it, there could be pops when the stream starts.

This reverts commit c3278fe1

Bug: 437183295
Test: atest test_flowgraph#module_ramp_linear
Test: OboeTester Test Output
Test: atest AAudioTests
Flag: EXEMPT bugfix
Change-Id: Ied53e7ec2b452bcf72f038763204dff8684e664a