ASoC: SOF: debug: fix possible memory leak in sof_dfsentry_write()

'string' is malloced in sof_dfsentry_write() and should be freed
before leaving from the error handling cases, otherwise it will cause
memory leak.

Fixes: 091c12e1f5 ("ASoC: SOF: debug: add new debugfs entries for IPC flood test")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20190705081637.157169-1-weiyongjun1@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/debug.c

@@ -162,7 +162,7 @@ static ssize_t sof_dfsentry_write(struct file *file, const char __user *buffer,
 	else
 		ret = kstrtoul(string, 0, &ipc_count);
 	if (ret < 0)
-		return ret;
+		goto out;
 
 	/* limit max duration/ipc count for flood test */
 	if (flood_duration_test) {
@@ -191,7 +191,7 @@ static ssize_t sof_dfsentry_write(struct file *file, const char __user *buffer,
 				    "error: debugfs write failed to resume %d\n",
 				    ret);
 		pm_runtime_put_noidle(sdev->dev);
-		return ret;
+		goto out;
 	}
 
 	/* flood test */