CRAS: Initialize x_prev in dcblock_process

Set correct inital value of x_prev to remove the DC \
and slope in the beginning of the recorded waveform

BUG=b:133722255
TEST=1. Make sure DC filter is applied \
     2. powerd_dbus_suspend \
     3. arecord -f dat -d 10 /tmp/test-cras.wav \
     4. The peak in the beginning of the recorded waveform \
     should be removed

Change-Id: Ic268999141ae9c291ec2984304f1242b6e0a91ed
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/adhd/+/1832956
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org>
Tested-by: Judy Hsiao <judyhsiao@chromium.org>
Commit-Queue: Judy Hsiao <judyhsiao@chromium.org>
1 file changed