cleanup: apply constness to read-only iterators

Apply const to read-only iterators to indicate intent more clearly.

Change-Id: Ic14304c69361da203d3d3a900180bd54346acc87
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/sensors/builder.cpp b/sensors/builder.cpp
index 881a9c2..7927dd0 100644
--- a/sensors/builder.cpp
+++ b/sensors/builder.cpp
@@ -42,7 +42,7 @@
     auto& HostSensorBus = mgmr.getHostBus();
     auto& PassiveListeningBus = mgmr.getPassiveBus();
 
-    for (auto& it : config)
+    for (const auto& it : config)
     {
         std::unique_ptr<ReadInterface> ri;
         std::unique_ptr<WriteInterface> wi;