Allow disabling PID loops at runtime

<design concept>
Add the map of object enable interface to pid loops
in the zone then we can disable/enable each pid loop
process in a zone by dbus command.

[note]
Enable = true  : enable process (default)
Enable = false : disable process

Tested:
In this case: we set Enable = false to disable
pidloop:Zone_Temp_0, and see how it affects
the zone final pwm, when pidloop: Zone_Temp_0
in zone 0 is disabled.

then even we are trying to heat up the temperature
of a sensor: Temp_0 in pidloop: Zone_Temp_0, this
set point of the pidloop will not be taken into the
calculation for the final set point of the whole zone.

```
<service object>
root@openbmc:/tmp# busctl tree xyz.openbmc_project.State.FanCtrl
`-/xyz
  `-/xyz/openbmc_project
    `-/xyz/openbmc_project/settings
      `-/xyz/openbmc_project/settings/fanctrl
        |-/xyz/openbmc_project/settings/fanctrl/zone0
        | |-/xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp
        | |-/xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp_0
        | `-/xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp_1

====Enable process for pidloop:Zone_Temp_0 with p-switch temperature sensor:Temp_0 at runtime====
root@openbmc:~# busctl introspect xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp_0
NAME                                TYPE      SIGNATURE RESULT/VALUE FLAGS
xyz.openbmc_project.Object.Enable   interface -         -            -
.Enabled                            property  b         true         emits-change writable

====Disable process for pidloop:Zone_Temp_0 with p-switch temperature sensor: Temp_0====
root@openbmc:~# busctl set-property xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp_0 xyz.openbmc_project.Object.Enable Enabled b false
root@openbmc:~# busctl introspect xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp_0
NAME                                TYPE      SIGNATURE RESULT/VALUE FLAGS
xyz.openbmc_project.Object.Enable   interface -         -            -
.Enabled                            property  b         false        emits-change writable
```

when Disable the process of the pidloop: Zone_Temp_0,
the requester switches from Zone_Temp_0 to the others,
when you enable the pidloop: Zone_Temp_0, the setpoint
of Zone_Temp_0 will be take into consideration again

Change-Id: I95ae700144f0d16049fff8b309f05ae690a7ef72
Signed-off-by: ykchiu <Chiu.YK@inventec.com>
diff --git a/pid/zone.hpp b/pid/zone.hpp
index b985f5f..9604c73 100644
--- a/pid/zone.hpp
+++ b/pid/zone.hpp
@@ -11,6 +11,7 @@
 #include <sdbusplus/bus.hpp>
 #include <sdbusplus/server.hpp>
 #include <xyz/openbmc_project/Control/Mode/server.hpp>
+#include <xyz/openbmc_project/Object/Enable/server.hpp>
 
 #include <fstream>
 #include <iostream>
@@ -24,6 +25,9 @@
 using ServerObject = typename sdbusplus::server::object_t<T...>;
 using ModeInterface = sdbusplus::xyz::openbmc_project::Control::server::Mode;
 using ModeObject = ServerObject<ModeInterface>;
+using ProcessInterface =
+    sdbusplus::xyz::openbmc_project::Object::server::Enable;
+using ProcessObject = ServerObject<ProcessInterface>;
 
 namespace pid_control
 {
@@ -98,6 +102,10 @@
     bool manual(bool value) override;
     /* Method for reading whether in fail-safe mode over dbus */
     bool failSafe() const override;
+    /* Method for control process for each loop at runtime */
+    void addPidControlProcess(std::string name, sdbusplus::bus_t& bus,
+                              std::string objPath, bool defer);
+    bool isPidProcessEnabled(std::string name);
 
   private:
     template <bool fanSensorLogging>
@@ -196,6 +204,8 @@
 
     std::vector<std::unique_ptr<Controller>> _fans;
     std::vector<std::unique_ptr<Controller>> _thermals;
+
+    std::map<std::string, std::unique_ptr<ProcessObject>> _pidsControlProcess;
 };
 
 } // namespace pid_control