ASoC: sigmadsp: switch to use kmemdup_nul() helper

Use kmemdup_nul() helper instead of open-coding to
simplify the code.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220825123525.1845695-1-yangyingliang@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/sigmadsp.c

@@ -227,13 +227,11 @@ static int sigma_fw_load_control(struct sigmadsp *sigmadsp,
 	if (!ctrl)
 		return -ENOMEM;
 
-	name = kzalloc(name_len + 1, GFP_KERNEL);
+	name = kmemdup_nul(ctrl_chunk->name, name_len, GFP_KERNEL);
 	if (!name) {
 		ret = -ENOMEM;
 		goto err_free_ctrl;
 	}
-	memcpy(name, ctrl_chunk->name, name_len);
-	name[name_len] = '\0';
 	ctrl->name = name;
 
 	/*