ALSA: hda - add flags and routines to get devices selection info for DP1.2 MST

This patch adds flags and routines to get device list & selection info on
a pin.

To support Display Port 1.2 multi-stream transport (MST) over single DP port,
a pin can support multiple devices. Please refer to HD-A spec Document Change
Notificaton HDA040-A.

A display audio codec can set flag "dp_mst" in its patch, indicating its pins
can support MST. But at runtime, a pin may not be multi-streaming capable and
report the device list is empty, depending on Gfx driver configuration.

Signed-off-by: Mengdong Lin <mengdong.lin@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
ALSA: hda - add device list & select info of display pins to codec proc file

If a display codec supports multi-stream transport on the pins, the pin's
device list length and device entries will be exposed to codec proc file.

Signed-off-by: Mengdong Lin <mengdong.lin@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
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>
ALSA: hda - add device entry and inactive flag to unsolicited response

This patch adds two fields to unsolicited response, according to spec HDA040-A:
- Device Entry (bit 20:15)
- Inactive (bit 2)
and show the info in debug message.

Signed-off-by: Mengdong Lin <mengdong.lin@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
ALSA: hda - Simplify CONFIG_SND_HDA_I915 condition

CONFIG_SND_HDA_I915 doesn't have to be user-selectable as this is almost
mandatory when i915 driver is available.  Let's enable it always when
CONFIG_DRM_I915 is set, so that user won't be bothered by useless
questions.

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