ASoC: Intel: Atom: remove useless assignment

Fix cppcheck warning:

sound/soc/intel/atom/sst/sst.c:52:20: style: Variable 'size' is
assigned a value that is never used. [unreadVariable]
 unsigned int size = 0;
                   ^

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200813200147.61990-9-pierre-louis.bossart@linux.intel.com


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