ASoC: Intel: Atom: compress: remove redundant assignment

Fix cppcheck warning:

sound/soc/intel/atom/sst-mfld-platform-compress.c:46:14: style:
Variable 'ret_val' is assigned a value that is never
used. [unreadVariable]
 int ret_val = 0;
             ^
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200813200147.61990-3-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/atom/sst-mfld-platform-compress.c

@@ -42,8 +42,7 @@ static void sst_drain_notify(void *arg)
 static int sst_platform_compr_open(struct snd_soc_component *component,
 				   struct snd_compr_stream *cstream)
 {
-
-	int ret_val = 0;
+	int ret_val;
 	struct snd_compr_runtime *runtime = cstream->runtime;
 	struct sst_runtime_stream *stream;