Since we can query the playback stream power state directly we do not
need to infer if it is powered up from the timer being scheduled.  Doing
this avoids problems that previously existed with streams being
incorrectly determined to be powered up caused when the timer is
scheduled when streams are closed after being partially set up.
Reported-by: NNobin Mathew <nobin.mathew@gmail.com>
Reported-by: NJukka Hynninen <ext-jukka.hynninen@vaisala.com>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>