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 uint32_t out_get_sample_rate(const struct audio_stream *stream)
{
 struct stream_out *out = (struct stream_out *)stream;

 return out->sample_rate;
}

static uint32_t out_get_sample_rate(const struct audio_stream *stream)
{
 struct stream_out *out = (struct stream_out *)stream;

 return out->sample_rate;
}
