Do not reset charge_max_level during CHG_LIMIT_GET_LIMIT

Fixes #6.

Author: DHowett

board/hx20/battery.c

@@ -363,8 +363,9 @@ static enum ec_status cmd_charging_limit_control(struct host_cmd_handler_args *a
 		charging_maximum_level = charging_maximum_level | CHG_LIMIT_OVERRIDE;
 
 	if (p->modes & CHG_LIMIT_GET_LIMIT) {
-		system_get_bbram(SYSTEM_BBRAM_IDX_CHG_MAX, &charging_maximum_level);
-		r->max_percentage = charging_maximum_level;
+		uint8_t max = 0;
+		system_get_bbram(SYSTEM_BBRAM_IDX_CHG_MAX, &max);
+		r->max_percentage = max;
 		args->response_size = sizeof(*r);
 	}