ALSA: hda - Fix GPIO LED setup for IDT 92HD75 codecs

Some HP laptops with IDT 92HD75 codecs may use a GPIO > 4 for the mute
LED, but currently the driver doesn't check this properly, and confuses
the mute LED behavior.  This ended up with the silent output  on some
HP laptops due to  having another GPIO used as external amp control.

This patch fixes the problem by checking the max GPIO count and
comparing with the given value from DMI entry instead of magic fixed
value 4 and 8, and adding a new field to indicate the VREF mute-LED
behavior.

Reported-and-tested-by: Vitaliy Kulikov <Vitaliy.Kulikov@idt.com>
Cc: <stable@kernel.org> [v3.1]
Signed-off-by: Takashi Iwai <tiwai@suse.de>