Write the clang-tidy file OpenBMC needs

Now that CI can handle clang-tidy, and a lot of the individual fixes
have landed for the various static analysis checks, lets see how close
we are.

This includes bringing a bunch of the code up to par with the checks
that require.  Most of them fall into the category of extraneous else
statements, const correctness problems, or extra copies.

Tested:
CI only.  Unit tests pass.

Signed-off-by: Ed Tanous <ed@tanous.net>
Change-Id: I9fbd346560a75fdd3901fa40c57932486275e912
diff --git a/redfish-core/lib/ethernet.hpp b/redfish-core/lib/ethernet.hpp
index 3494ede..1fb8783 100644
--- a/redfish-core/lib/ethernet.hpp
+++ b/redfish-core/lib/ethernet.hpp
@@ -158,11 +158,11 @@
     {
         return "xyz.openbmc_project.Network.EthernetInterface.DHCPConf.both";
     }
-    else if (isIPv4)
+    if (isIPv4)
     {
         return "xyz.openbmc_project.Network.EthernetInterface.DHCPConf.v4";
     }
-    else if (isIPv6)
+    if (isIPv6)
     {
         return "xyz.openbmc_project.Network.EthernetInterface.DHCPConf.v6";
     }
@@ -183,10 +183,7 @@
         {
             return "IPv4LinkLocal";
         }
-        else
-        {
-            return "LinkLocal";
-        }
+        return "LinkLocal";
     }
     if (inputOrigin == "xyz.openbmc_project.Network.IP.AddressOrigin.DHCP")
     {
@@ -194,10 +191,7 @@
         {
             return "DHCP";
         }
-        else
-        {
-            return "DHCPv6";
-        }
+        return "DHCPv6";
     }
     if (inputOrigin == "xyz.openbmc_project.Network.IP.AddressOrigin.SLAAC")
     {
@@ -678,10 +672,7 @@
                         // Continuity not preserved
                         return false;
                     }
-                    else
-                    {
-                        (*bits)++;
-                    }
+                    (*bits)++;
                 }
                 else
                 {
@@ -1567,12 +1558,9 @@
                         messages::resourceCannotBeDeleted(asyncResp->res);
                         return;
                     }
-                    else
-                    {
-                        messages::propertyValueFormatError(
-                            asyncResp->res, thisJson.dump(), pathString);
-                        return;
-                    }
+                    messages::propertyValueFormatError(
+                        asyncResp->res, thisJson.dump(), pathString);
+                    return;
                 }
 
                 if (thisJson.is_null())
@@ -1704,12 +1692,9 @@
                         messages::resourceCannotBeDeleted(asyncResp->res);
                         return;
                     }
-                    else
-                    {
-                        messages::propertyValueFormatError(
-                            asyncResp->res, thisJson.dump(), pathString);
-                        return;
-                    }
+                    messages::propertyValueFormatError(
+                        asyncResp->res, thisJson.dump(), pathString);
+                    return;
                 }
 
                 if (thisJson.is_null())
@@ -2099,10 +2084,7 @@
         {
             return false;
         }
-        else
-        {
-            return true;
-        }
+        return true;
     }
 
     /**