ASoC: Intel: Skylake: sst-utils: remove redundant assignment

Fix cppcheck warning:

sound/soc/intel/skylake/skl-sst-utils.c:240:10: style: Variable 'ret'
is assigned a value that is never used. [unreadVariable]
 int ret = 0;
         ^

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200813200147.61990-19-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>