ALSA: hda: ext: simplify logic for stream assignment

The logic is needlessly complicated, the basic rule is:

The host streams can be found by checking the 'opened' boolean.
The link streams can be found by checking the 'link_locked' boolean.

Once a stream is found, it can be unconditionally decoupled. The
snd_hdac_ext_stream_decouple_locked() routine will make sure the
register status is modified as needed and the 'decoupled' boolean set.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20220919121041.43463-7-pierre-louis.bossart@linux.intel.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>