ALSA: hda - Avoid unnecessary verbs to clear PCM formats

Since really_cleanup_stream() is called from both purity_inactive_streams()
and hda_cleanup_all_streams(), the verbs to clear the PCM channel and
format may be called multiple times unnecessarily.

This patch adds checks to skip these unneeded verbs.

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