ALSA: hda - Minor cleanup/fixes for patch_sigmatel.c fixup transition

- spec->hp_detect has to be overridden in HDA_FIXUP_ACT_PARSE, not in
  PRE_PARSE.
- Remove err == 0 check but return directly -EINVAL from
  stac92xx_parse_auto_config()
- Set spec->default_polarity for 92HD71bxx
- Some code shuffles

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