include: add missing headers

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I6b26a1bea2aae173b57dbd8affa0ba4991b1c9bb
diff --git a/include/PSUSensor.hpp b/include/PSUSensor.hpp
index f7ed88f..c0ebe6a 100644
--- a/include/PSUSensor.hpp
+++ b/include/PSUSensor.hpp
@@ -4,7 +4,9 @@
 #include "Thresholds.hpp"
 #include "sensor.hpp"
 
+#include <memory>
 #include <sdbusplus/asio/object_server.hpp>
+#include <string>
 
 class PSUSensor : public Sensor
 {