ASoC: SOF: topology: check errors when parsing LED tokens

sof_parse_tokens() returns a value that is checked on every call
except for LED tokens, fix with explicit test.

Detected with cppcheck warning:

sound/soc/sof/topology.c:973:6: style: Variable 'ret' is assigned a
value that is never used. [unreadVariable]
 ret = sof_parse_tokens(scomp, &scontrol->led_ctl, led_tokens,
     ^

Fixes: 5d43001a ("ASoC: SOF: acpi led support for switch controls")
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20191011164312.7988-5-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/topology.c

@@ -963,6 +963,11 @@ static int sof_control_load_volume(struct snd_soc_component *scomp,
 	ret = sof_parse_tokens(scomp, &scontrol->led_ctl, led_tokens,
 			       ARRAY_SIZE(led_tokens), mc->priv.array,
 			       le32_to_cpu(mc->priv.size));
+	if (ret != 0) {
+		dev_err(sdev->dev, "error: parse led tokens failed %d\n",
+			le32_to_cpu(mc->priv.size));
+		return ret;
+	}
 
 	dev_dbg(sdev->dev, "tplg: load kcontrol index %d chans %d\n",
 		scontrol->comp_id, scontrol->num_channels);