ALSA: hda/realtek - Add missing initialization of multi-io routes

The paths used for multi-io haven't been initialized properly, so
far.  It's usually no big matter because the pins are set to input as
default, but it's still cleaner to initialize the paths properly.

Now with the path active/inactive check, we can do it easily.

Signed-off-by: Takashi Iwai <tiwai@suse.de>