Apply misc-include-cleaner fixes

misc-include-cleaner seems to have found a lot more things all of a
sudden.  Unclear why the result has changed, but we can just fix the
issues.

Tested: Clang-tidy now passes.  Code compiles.

Change-Id: Iab045cc183f0daef663b4d5ac901200a42807987
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/src/psu/PSUEvent.hpp b/src/psu/PSUEvent.hpp
index d761f45..75c89f2 100644
--- a/src/psu/PSUEvent.hpp
+++ b/src/psu/PSUEvent.hpp
@@ -22,9 +22,11 @@
 #include <boost/asio/random_access_file.hpp>
 #include <boost/asio/steady_timer.hpp>
 #include <boost/container/flat_map.hpp>
+#include <sdbusplus/asio/connection.hpp>
 #include <sdbusplus/asio/object_server.hpp>
 
 #include <array>
+#include <cstddef>
 #include <memory>
 #include <set>
 #include <string>