audio_AudioBasicExternalMicrophone: Remove more data from the head

Remove 1.5 seconds data from the head to avoid the artifact of codec
initialization.

BUG=None
TEST=run audio_AudioBasicExternalMicrophone test on squawks

Change-Id: I1ad560e8c0911b32d6f75961f62a1f53e1783cab
Reviewed-on: https://chromium-review.googlesource.com/269251
Reviewed-by: Tom Tam <waihong@google.com>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
Commit-Queue: Cheng-Yi Chiang <cychiang@chromium.org>
1 file changed