Fixed the bug that multiple capture streams conflict on Realtek codec
routines.
Also, this adds a framework to enable the alternative playback stream,
e.g. for VoIP.  It's not fully implemented yet, though.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NJaroslav Kysela <perex@perex.cz>