Take boost error_code by reference

By convention, we should be following boost here, and passing error_code
by reference, not by value.  This makes our code consistent, and removes
the need for a copy in some cases.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Id42ea4a90b6685a84818b87d1506c11256b3b9ae
diff --git a/redfish-core/lib/bios.hpp b/redfish-core/lib/bios.hpp
index 74a22d4..1153516 100644
--- a/redfish-core/lib/bios.hpp
+++ b/redfish-core/lib/bios.hpp
@@ -71,7 +71,7 @@
     }
 
     crow::connections::systemBus->async_method_call(
-        [asyncResp](const boost::system::error_code ec) {
+        [asyncResp](const boost::system::error_code& ec) {
         if (ec)
         {
             BMCWEB_LOG_ERROR << "Failed to reset bios: " << ec;