Add associations for pwm

Pwm doesn't inheirt from Sensor as it is special, so
it needs it to be added seperate.

Tested: Saw associations on dbus

Change-Id: I2178e9346dcae845b47a013a2cc15f62e9ed9b31
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/include/sensor.hpp b/include/sensor.hpp
index a6bf2b1..607eb3d 100644
--- a/include/sensor.hpp
+++ b/include/sensor.hpp
@@ -50,16 +50,7 @@
     void
         setInitialProperties(std::shared_ptr<sdbusplus::asio::connection>& conn)
     {
-        if (association)
-        {
-            using Association =
-                std::tuple<std::string, std::string, std::string>;
-            std::vector<Association> associations;
-            associations.push_back(
-                Association("inventory", "sensors", configurationPath));
-            association->register_property("associations", associations);
-            association->initialize();
-        }
+        createAssociation(association, configurationPath);
 
         sensorInterface->register_property("MaxValue", maxValue);
         sensorInterface->register_property("MinValue", minValue);