ASoC: fsl: fsl_spdif: fix kernel-doc

Fix W=1 warnings. kernel-doc syntax was not followed and missing parameter

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Link: https://lore.kernel.org/r/20200702192141.168018-5-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>