When an invalid NID is given, get_wcaps() returns zero as the error,
but get_wcaps_type() takes it as the normal value and returns a bogus
AC_WID_AUD_OUT value.  This confuses the parser.

With this patch, get_wcaps_type() returns -1 when value 0 is given,
i.e. an invalid NID is passed to get_wcaps().

Bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=740118

Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>