When initializing the output paths, we assumed the input amps have
almost two inputs blindly.  It's not only generic but even incorrect
for some codecs like ALC268 & co.  Also, the same assumption (two
sources) exists for the bind input-amp controls.

This patch changes the codes in these places to handle the input
connections in a more generic way.
Signed-off-by: Takashi Iwai <tiwai@suse.de>