regmap: core: Report registers in hex when we can't cache

This seems to be the most common way of reporting register numbers, it's
certainly what we do for trace.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 52069d2..810f509 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -814,7 +814,7 @@
 					     ival);
 			if (ret) {
 				dev_err(map->dev,
-				   "Error in caching of register: %u ret: %d\n",
+					"Error in caching of register: %x ret: %d\n",
 					reg + i, ret);
 				return ret;
 			}