Use wait_event_cmd() macro and simplify snd_power_ref_wait()
implementation.  This may also cover possible races in the current
open code, too.
Reviewed-by: NJaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220119091050.30125-1-tiwai@suse.deSigned-off-by: NTakashi Iwai <tiwai@suse.de>