ALSA: hda - Don't add elements of other codecs to vmaster slave

When a virtual mater control is created, the driver looks for slave
elements from the assigned card instance.  But this may include the
elements of other codecs when multiple codecs are on the same HD-audio
bus.  This works at the first time, but it'll give Oops when it's once
freed and re-created via reconfig sysfs.

This patch changes the element-look-up strategy to limit only to the
mixer elements of the same codec.

Reported-by: David Henningsson <david.henningsson@canonical.com>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>