ASoC: Intel: Skylake: Fix missing sentinel in sst_acpi_mach

To make it consistent, add sentinel for sst_cnl_devdata also.

Signed-off-by: Guneshwor Singh <guneshwor.o.singh@intel.com>
Acked-By: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>