ALSA: snd-opti9xx: fixes for MED3931 card (opti931)

MED3931 card did not work (failed with "OPTI chip not found") because
snd-opti9xx gets mc_indir_index from pnp by adding 2 to the pnp-reported port.
It probably works for some cards but not for this one. Datasheet says that
the port is always at 0xe?e so just force the lowest nibble to be 0xe.

Also this card powers up with (ugly) 3D sound enabled. As there's no mixer
control for this, just disable it.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>