aaudio: fix framesWritten for Legacy INPUT

Was set to 2X framesRead on stop.
It turns out that AudioRecord::stop() does NOT reset getPosition()
to zero. But AudioRecord::start() does.
So the logic handling the reset had to move to the start code.

Bug: 121196899
Test: test_return_stop -i -n
Change-Id: I93635f9ba501b71b99b1df34c7920f7bfea5ca88