ASoC: topology: free link string in error

Some strings are allocated by kstrdup, but not freed when error
happened.

Signed-off-by: Bard liao <yung-chuan.liao@linux.intel.com>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>