ALSA: hda/realtek: Enable HP amp and mute LED on HP Folio 9480m [v3]

This laptop needs GPIO4 pulled high to enable the headphone amplifier,
and has a mute LED on GPIO3. I modelled the patch on the existing
GPIO4 code which pulls the line low for the same purpose; this time,
the HP amp line is pulled high.

v2: Disable the headphone amplifier when no headphone is connected.
    Don't disable power savings to preserve the LED state.

v3: Remove headset-specific hooks and code; this is just a headphone.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>