ASoC: fixes to caching implementations

This patch takes fixes a number of bugs in the caching code used by
several ASoC codec drivers. Mostly off-by-one fixes.

Signed-off-by: Ian Molton <ian@mnementh.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/codecs/twl4030.c b/sound/soc/codecs/twl4030.c
index ddc9f37..f530c1e 100644
--- a/sound/soc/codecs/twl4030.c
+++ b/sound/soc/codecs/twl4030.c
@@ -125,6 +125,9 @@
 {
 	u8 *cache = codec->reg_cache;
 
+	if (reg >= TWL4030_CACHEREGNUM)
+		return -EIO;
+
 	return cache[reg];
 }