Sometimes (or rather often) BIOS sets the pin default configurations
obviously wrongly.  Looking through these failures, one common pattern
is to enable some dead pins that are usually marked as speaker pins.
In such a case, we can skip them if the pins don't have the output
capability.

In this patch, add a check for the valid pin cap bit for each parsed
pin, and filter out when it's invalid.

The fix was originally suggested by Raymond Yau.
Signed-off-by: Takashi Iwai <tiwai@suse.de>