ASoC: rt700: fix return value check in rt700_sdw_probe()

In case of error, the function devm_regmap_init() returns ERR_PTR() and
never returns NULL. The NULL test in the return value check should be
replaced with IS_ERR().

Fixes: 7d2a5f9a ("ASoC: rt700: add rt700 codec driver")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20200115143027.94364-1-weiyongjun1@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/rt700-sdw.c

@@ -460,8 +460,8 @@ static int rt700_sdw_probe(struct sdw_slave *slave,
 
 	regmap = devm_regmap_init(&slave->dev, NULL,
 		&slave->dev, &rt700_regmap);
-	if (!regmap)
-		return -EINVAL;
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
 
 	rt700_init(&slave->dev, sdw_regmap, regmap, slave);