Fix audio record pre-processing

proc_buf_out consistently initialized.
intermediate scratch buffers consistently initialized.
prevent read failure from overwriting memory.

Test: POC, CTS, camera record
Bug: 62873231
Change-Id: Ie26e12a419a5819c1c5c3a0bcf1876d6d7aca686
(cherry picked from commit 6d7b330c27efba944817e647955da48e54fd74eb)

static int set_voice_volume_l(struct audio_device *adev, float volume)
{
 int err = 0;
 (void)volume;

 if (adev->mode == AUDIO_MODE_IN_CALL) {
 /* TODO */
 }
 return err;
}

static int set_voice_volume_l(struct audio_device *adev, float volume)
{
 int err = 0;
 (void)volume;

 if (adev->mode == AUDIO_MODE_IN_CALL) {
 /* TODO */
 }
 return err;
}
