ASoC: Intel: Skylake: Shield against no-NHLT configurations

Some configurations expose no NHLT table at all within their
/sys/firmware/acpi/tables. To prevent NULL-dereference errors from
occurring, adjust probe flow and append additional safety checks in
functions involved in NHLT lifecycle.

Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200305145314.32579-5-cezary.rojewski@intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>