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 audio_format_t in_get_format(const struct audio_stream *stream)
{
 (void)stream;
 return AUDIO_FORMAT_PCM_16_BIT;
}

static audio_format_t in_get_format(const struct audio_stream *stream)
{
 (void)stream;
 return AUDIO_FORMAT_PCM_16_BIT;
}
