ASoC: compress: Only mute playback streams

Otherwise capture activity on a compressed DAI would mute any playback
on the same DAI.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Acked-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>