It should be programmed to "0" for HDMI or "1" for DisplayPort.

This enables DisplayPort audio for

- HP EliteBook 8460p
  (whose BIOS does not set the N_value_index bit for us)

- DisplayPort monitor hot plugged after boot
  (otherwise most BIOS will fill the N_value_index bit for us)
Tested-by: NRobert Lemaire <rlemaire@suse.com>
Reviewed-by: NKeith Packard <keithp@keithp.com>
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>