ALSA: hda/hdmi: fix silent stream for first playback to DP

ALSA: hda/hdmi: fix silent stream for first playback to DP

A problem exists in enabling silent stream when connection type is
DisplayPort. Silent stream programming is completed when a new DP
receiver is connected, but infoframe transmission does not actually
start until PCM is opened for the first time. This can result in audible
gap of multiple seconds. This only affects the first PCM open.

Fix the issue by properly assigning a converter to the silent stream,
and modifying the required stream ID programming sequence.

This change only affects Intel display audio codecs.

BugLink: https://github.com/thesofproject/linux/issues/2468
Fixes: d6857645c0cb ("ALSA: hda/hdmi: Add Intel silent stream support")
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20201210174445.3134104-1-kai.vehmanen@linux.intel.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>