ANDROID: goldfish_audio: Clear audio read buffer status after each read

The buffer_status field is interrupt updated. After every read request,
the buffer_status read field should be reset so that on the next loop
iteration we don't read a stale value and read data before the
device is ready.

Signed-off-by: “Joshua Lang” <joshualang@google.com>
Change-Id: I4943d5aaada1cad9c7e59a94a87c387578dabe86