ASoC: ad1836: fix a memory leak if another ad1836 is registered

ad1836 is allocated in ad1836_spi_probe() but is not freed if ad1836_register()
return -EINVAL (if another ad1836 is registered).

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Barry Song <21cnbao@gmail.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/ad1836.c

@@ -272,6 +272,7 @@ static int ad1836_register(struct ad1836_priv *ad1836)
 
 	if (ad1836_codec) {
 		dev_err(codec->dev, "Another ad1836 is registered\n");
+		kfree(ad1836);
 		return -EINVAL;
 	}