ALSA: hda - Haswell codec exposes device list/select info on pins

This patch is only to allow codec proc file to expose devices list/select info
for Haswell codec pins.

Since Haswell Gfx driver cannot support DP1.2 MST now, so all pins' device list
is empty, meaning no pin is multi-streaming capaple.

Signed-off-by: Mengdong Lin <mengdong.lin@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>