CRAS: input_data - Use the correct offset to process APM

Whenever we process input_data's float buffer, should use the
unchanged stream offset.
Fix the bug that we pass the audio area's offset to APM process
function. This is incorrect in rare cases when the stream offset
gets clipped by area's frame count.

BUG=chromium:973745
TEST=Run audio_CrasDevSwitchStress.input to verify input buffer
level in CRAS doesn't go super high.

Change-Id: I088a037a6496f1a7f69ade37195fb65c6286bb71
Reviewed-on: https://chromium-review.googlesource.com/1670416
Tested-by: Hsinyu Chao <hychao@chromium.org>
Commit-Ready: Hsinyu Chao <hychao@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
3 files changed