Fix Association interface

Mapper changed to only allow the new interface, update
to it.

Tested: Mapper showed all associations

Change-Id: I8b252c70e9f27b083a438393c731fbeb3e2ca0e5
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/src/PwmSensor.cpp b/src/PwmSensor.cpp
index c33f05c..063c359 100644
--- a/src/PwmSensor.cpp
+++ b/src/PwmSensor.cpp
@@ -115,8 +115,7 @@
     controlInterface->initialize();
 
     association = objectServer.add_interface(
-        "/xyz/openbmc_project/sensors/fan_pwm/" + name,
-        "org.openbmc.Associations");
+        "/xyz/openbmc_project/sensors/fan_pwm/" + name, association::interface);
     createAssociation(association, sensorConfiguration);
 }
 PwmSensor::~PwmSensor()