drivers/regulator/core.c: Fixes mapping inside regulator_mode_to_status() and makes it returning -EINVAL on invalid input.

[Krystian Garbaciak <dd.diasemi@gmail.com>]

Minor fix that makes the function working correctly with
REGULATOR_MODE_STANDBY as parameter.
Also, on invalid input (bad mode), it is better to return -EINVAL,
instead of meaningless 0 value (which actually is interpreted as
REGULATOR_STATUS_OFF).

--- 
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 938398f..45aa874 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2484,10 +2484,10 @@ int regulator_mode_to_status(unsigned int mode)
 		return REGULATOR_STATUS_NORMAL;
 	case REGULATOR_MODE_IDLE:
 		return REGULATOR_STATUS_IDLE;
-	case REGULATOR_STATUS_STANDBY:
+	case REGULATOR_MODE_STANDBY:
 		return REGULATOR_STATUS_STANDBY;
 	default:
-		return 0;
+		return -EINVAL;
 	}
 }
 EXPORT_SYMBOL_GPL(regulator_mode_to_status);