audio: split pcm_ops function get_buffer_in

Split off pcm_ops function run_buffer_in from get_buffer_in and
call run_buffer_in before get_buffer_in.

The next patch only needs the generic buffer management part
from audio_generic_get_buffer_in().

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 9315afe5-5958-c0b4-ea1e-14769511a9d5@t-online.de
Message-Id: <20210110100239.27588-8-vr_qemu@t-online.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>