ASoC: dapm: Modify widget stream name according to prefix

When there is prefix specified, currently we will add this prefix in
widget->name, but not in widget->sname.
it causes failure at snd_soc_dapm_link_dai_widgets:

if (!w->sname || !strstr(w->sname, dai_w->name))

because dai_w->name has prefix added, but w->sname does not.
We should also add prefix for stream name

Signed-off-by: Koro Chen <koro.chen@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org