platform-mc: Add sensor manager

Added sensor_manager class. The sensor_manager class manages the timing
of sensor polling.

tested: Verified on ast2600 EVB which is connected to a PLDM device
over I2C. bmcweb can display the state of numeric sensor.

Signed-off-by: Gilbert Chen <gilbert.chen@arm.com>
Signed-off-by: Thu Nguyen <thu@os.amperecomputing.com>
Change-Id: I4257f823ea26d7fdb322cc82d847e94db056258c
diff --git a/pldmd/pldmd.cpp b/pldmd/pldmd.cpp
index 13d28f2..8637a15 100644
--- a/pldmd/pldmd.cpp
+++ b/pldmd/pldmd.cpp
@@ -196,6 +196,8 @@
     auto& bus = pldm::utils::DBusHandler::getBus();
     sdbusplus::server::manager_t objManager(bus,
                                             "/xyz/openbmc_project/software");
+    sdbusplus::server::manager_t sensorObjManager(
+        bus, "/xyz/openbmc_project/sensors");
 
     InstanceIdDb instanceIdDb;
     dbus_api::Requester dbusImplReq(bus, "/xyz/openbmc_project/pldm",