ALSA: hda/hdmi: Drop bogus check at closing a stream

Some users reported the kernel WARNING with stack traces from
hdmi_pcm_close(), and it's the line checking the per_cvt->assigned
flag.  This used to be a valid check in the past because the flag was
turned on/off only at opening and closing a PCM stream.  Meanwhile,
since the introduction of the silent-stream mode, this flag may be
turned on/off at the monitor connection/disconnection time, which
isn't always associated with the PCM open/close.  Hence this may lead
to the inconsistent per_cvt->assigned flag at closing.

As the check itself became almost useless and confuses users as if it
were a serious problem, just drop the check.

Fixes: b1a5039759 ("ALSA: hda/hdmi: fix silent stream for first playback to DP")
Cc: <stable@vger.kernel.org>
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=210987
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20210211083139.29531-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/patch_hdmi.c

@@ -2130,7 +2130,6 @@ static int hdmi_pcm_close(struct hda_pcm_stream *hinfo,
 			goto unlock;
 		}
 		per_cvt = get_cvt(spec, cvt_idx);
-		snd_BUG_ON(!per_cvt->assigned);
 		per_cvt->assigned = 0;
 		hinfo->nid = 0;