nvmes: add Availability interface

Add Availability interface.
When PwrGoodPin is low, Set Available property to false to indicate
this sensor is currently unavilable due to power loss.

Tested on Bletchley:

- PwrGoodPin is low
root@bletchley:~# busctl introspect xyz.openbmc_project.nvme.manager \
> /xyz/openbmc_project/sensors/temperature/nvme6 \
> xyz.openbmc_project.Sensor.Value
NAME                             TYPE      SIGNATURE RESULT/VALUE                             FLAGS
.MaxValue                        property  d         127                                      emits-change writable
.MinValue                        property  d         -127                                     emits-change writable
.Unit                            property  s         "xyz.openbmc_project.Sensor.Value.Uni... emits-change writable
.Value                           property  d         -127                                     emits-change writable
root@bletchley:~# busctl introspect xyz.openbmc_project.nvme.manager \
> /xyz/openbmc_project/sensors/temperature/nvme6 \
> xyz.openbmc_project.State.Decorator.Availability
NAME                                             TYPE      SIGNATURE RESULT/VALUE FLAGS
.Available                                       property  b         false        emits-change writable

- PwrGoodPin is high
root@bletchley:~# busctl introspect xyz.openbmc_project.nvme.manager \
> /xyz/openbmc_project/sensors/temperature/nvme6 \
> xyz.openbmc_project.Sensor.Value
NAME                             TYPE      SIGNATURE RESULT/VALUE                             FLAGS
.MaxValue                        property  d         127                                      emits-change writable
.MinValue                        property  d         -127                                     emits-change writable
.Unit                            property  s         "xyz.openbmc_project.Sensor.Value.Uni... emits-change writable
.Value                           property  d         33                                       emits-change writable
root@bletchley:~# busctl introspect xyz.openbmc_project.nvme.manager \
> /xyz/openbmc_project/sensors/temperature/nvme6 \
> xyz.openbmc_project.State.Decorator.Availability
NAME                                             TYPE      SIGNATURE RESULT/VALUE FLAGS
.Available                                       property  b         true         emits-change writable

Signed-off-by: Potin Lai <potin.lai@quantatw.com>
Change-Id: I0b621ae619dde85607c635912c7230bbe9de22ac
diff --git a/nvmes.hpp b/nvmes.hpp
index e11c891..92dfc6f 100644
--- a/nvmes.hpp
+++ b/nvmes.hpp
@@ -4,6 +4,7 @@
 #include <xyz/openbmc_project/Sensor/Threshold/Critical/server.hpp>
 #include <xyz/openbmc_project/Sensor/Threshold/Warning/server.hpp>
 #include <xyz/openbmc_project/Sensor/Value/server.hpp>
+#include <xyz/openbmc_project/State/Decorator/Availability/server.hpp>
 
 namespace phosphor
 {
@@ -18,8 +19,12 @@
 using WarningInterface =
     sdbusplus::xyz::openbmc_project::Sensor::Threshold::server::Warning;
 
-using NvmeIfaces = sdbusplus::server::object_t<ValueIface, CriticalInterface,
-                                               WarningInterface>;
+using AvailabilityInterface =
+    sdbusplus::xyz::openbmc_project::State::Decorator::server::Availability;
+
+using NvmeIfaces =
+    sdbusplus::server::object_t<ValueIface, CriticalInterface, WarningInterface,
+                                AvailabilityInterface>;
 
 class NvmeSSD : public NvmeIfaces
 {
@@ -51,6 +56,8 @@
                             int8_t warningHigh, int8_t warningLow);
     /** @brief Set Sensor Max/Min value to D-bus at beginning */
     void setSensorMaxMin(int8_t maxValue, int8_t minValue);
+    /** @brief Set Sensor Availability to D-bus */
+    void setSensorAvailability(bool avail);
 
   private:
     sdbusplus::bus_t& bus;