ASoC: topology: Fix error return code in soc_tplg_dapm_widget_create()

Fix to return error code -ENOMEM instead of 0 when failed to create
widget, as done elsewhere in this function.

Fixes: 8a978234 ("ASoC: topology: Add topology core")
Signed-off-by: Wei Yongjun <weiyj.lk@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>