ASoC: Intel: Skylake: Release FW ctx in cleanup

Saved firmware ctx was not never released, so release Firmware
ctx in cleanup routine.

Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>