ALSA: hda: remove unused quirk for inverted mute led

Commit b99a776d removed all effects of
the STAC92HD83* model quirk "hp". However, it left the model selection
and documentation behind, confusing users with inverted mute
leds. Completely remove this quirk and its documentation.

Signed-off-by: Gustavo Maciel Dias Vieira <gustavo@sagui.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>