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/builder.cpp b/pid/builder.cpp
index d7a60b4..08526fa 100644
--- a/pid/builder.cpp
+++ b/pid/builder.cpp
@@ -44,6 +44,11 @@
     return std::string(objectPath) + std::to_string(zone);
 }
 
+static std::string getPidControlPath(int64_t zone, std::string pidname)
+{
+    return std::string(objectPath) + std::to_string(zone) + "/" + pidname;
+}
+
 std::unordered_map<int64_t, std::shared_ptr<ZoneInterface>>
     buildZones(const std::map<int64_t, conf::PIDConf>& zonePids,
                std::map<int64_t, conf::ZoneConfig>& zoneConfigs,
@@ -109,6 +114,9 @@
                     getThermalType(info.type));
 
                 zone->addThermalPID(std::move(pid));
+                zone->addPidControlProcess(name, modeControlBus,
+                                           getPidControlPath(zoneId, name),
+                                           deferSignals);
             }
             else if (info.type == "stepwise")
             {
@@ -120,6 +128,9 @@
                 auto stepwise = StepwiseController::createStepwiseController(
                     zone.get(), name, inputs, info.stepwiseInfo);
                 zone->addThermalPID(std::move(stepwise));
+                zone->addPidControlProcess(name, modeControlBus,
+                                           getPidControlPath(zoneId, name),
+                                           deferSignals);
             }
 
             std::cerr << "inputs: ";