ALSA: pcm: Fix pcm_class sysfs output

commit 60b93030 upstream.

The pcm_class sysfs of each PCM substream gives only "none" since the
recent code change to embed the struct device.  Fix the code to point
directly to the embedded device object properly.

Fixes: ef46c7af ('ALSA: pcm: Embed struct device')
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>