fix warnings

Fix a couple warnings so we can use meson warning level 3.  Instances of
the following warnings are found and resolved:

  Wreorder
  Wsign-compare

Change-Id: Ia223b42aa6bf743cfa0e7042cc3d5a18977459be
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/src/Thresholds.cpp b/src/Thresholds.cpp
index bbddcde..fe5537f 100644
--- a/src/Thresholds.cpp
+++ b/src/Thresholds.cpp
@@ -120,7 +120,7 @@
                       std::shared_ptr<sdbusplus::asio::connection>& conn,
                       size_t thresholdCount)
 {
-    for (int ii = 0; ii < thresholdCount; ii++)
+    for (size_t ii = 0; ii < thresholdCount; ii++)
     {
         std::string thresholdInterface =
             baseInterface + ".Thresholds" + std::to_string(ii);