ASoC: max98373: Fix return check for devm_regmap_init_sdw()

devm_regmap_init_sdw() returns a valid pointer on success or ERR_PTR on
failure which should be checked with IS_ERR. Also use PTR_ERR for
returning error codes.
Reported-by: Takashi Iwai <tiwai@suse.de>
Fixes: 56a5b791 ("ASoC: codecs: max98373: add SoundWire support")
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200826163340.3249608-2-vkoul@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/max98373-sdw.c

@@ -838,8 +838,8 @@ static int max98373_sdw_probe(struct sdw_slave *slave,
 
 	/* Regmap Initialization */
 	regmap = devm_regmap_init_sdw(slave, &max98373_sdw_regmap);
-	if (!regmap)
-		return -EINVAL;
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
 
 	return max98373_init(slave, regmap);
 }