regmap: Return a sensible error code if we fail to read the cache

If a register isn't cached then let callers know that so they can fall
back or error handle appropriately.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
diff --git a/drivers/base/regmap/regcache-lzo.c b/drivers/base/regmap/regcache-lzo.c
index ad6af92..066aeec 100644
--- a/drivers/base/regmap/regcache-lzo.c
+++ b/drivers/base/regmap/regcache-lzo.c
@@ -232,7 +232,6 @@
 	size_t blksize, tmp_dst_len;
 	void *tmp_dst;
 
-	*value = 0;
 	/* index of the compressed lzo block */
 	blkindex = regcache_lzo_get_blkindex(map, reg);
 	/* register index within the decompressed block */
@@ -261,7 +260,8 @@
 	/* restore the pointer and length of the compressed block */
 	lzo_block->dst = tmp_dst;
 	lzo_block->dst_len = tmp_dst_len;
-	return 0;
+
+	return ret;
 }
 
 static int regcache_lzo_write(struct regmap *map,