ASoC: max98373: Add checks for devm_kcalloc

As the devm_kcalloc may return NULL pointer,
it should be better to check the return value
in order to avoid NULL poineter dereference.

Fixes: 349dd23931d1 ("ASoC: max98373: don't access volatile registers in bias level off")
Signed-off-by: Jiasheng Jiang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/codecs/max98373-i2c.c

···
 	max98373->cache = devm_kcalloc(&i2c->dev, max98373->cache_num,
 				       sizeof(*max98373->cache),
 				       GFP_KERNEL);
+	if (!max98373->cache) {
+		ret = -ENOMEM;
+		return ret;
+	}
 
 	for (i = 0; i < max98373->cache_num; i++)
 		max98373->cache[i].reg = max98373_i2c_cache_reg[i];