ALSA: hda - Fix multi-io channel mode management

The multi-io channels can vary not only from 1 to 6 but also may vary
from 6 to 8 or such.  At the same time, there are more speaker pins
available than the primary output pins.  So, we need three variables
to check: the minimum channel counts for primary outputs, the current
channel counts for primary outputs, and the minimum channel counts for
all outputs.

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