ASoC: wm_adsp: Add missing MODULE_LICENSE

Since MODULE_LICENSE is missing the module load fails,
so add this for module.

Signed-off-by: Praveen Diwakar <praveen.diwakar@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Reviewed-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org