ALSA: hda - Add EAPD fixup for ASUS Z99He laptop

The same fixup to enable EAPD is needed for ASUS Z99He with AD1986A
codec like another ASUS machine.

Reported-and-tested-by: Dmitry V. Zimin <pfzim@mail.ru>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
ALSA: hda - Add "eapd" model string for AD1986A codec

Also update the documentation to the latest state.

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