Populate AllowedPowerModes

AllowedPowerModes is a new dbus property that will be used by Redfish to
publish the supported modes.

'''
busctl -l introspect org.open_power.OCC.Control /xyz/openbmc_project/control/host0/power_mode
...
xyz.openbmc_project.Control.Power.Mode interface -         -                                                                                                                                                                                                                                                                                                                                                                                                                             -
.AllowedPowerModes                     property  as        3 "xyz.openbmc_project.Control.Power.Mode.PowerMode.MaximumPerformance" "xyz.openbmc_project.Control.Power.Mode.PowerMode.PowerSaving" "xyz.openbmc_project.Control.Power.Mode.PowerMode.Static" const
.PowerMode                             property  s         "xyz.openbmc_project.Control.Power.Mode.PowerMode.MaximumPerformance"                                                                                                                                                                                                                                                                                                                                                         emits-change writable
.SafeMode                              property  b         false                                                                                                                                                                                                                                                                                                                                                                                                                         emits-change
'''

Change-Id: I67ab6c2f8545c327dd7ab437f892ad5796a194c5
Signed-off-by: Chris Cain <cjcain@us.ibm.com>
diff --git a/powermode.hpp b/powermode.hpp
index 5363c2c..9a191f7 100644
--- a/powermode.hpp
+++ b/powermode.hpp
@@ -281,6 +281,12 @@
         event(event)
 #endif
     {
+        using Mode =
+            sdbusplus::xyz::openbmc_project::Control::Power::server::Mode;
+        ModeInterface::allowedPowerModes({Mode::PowerMode::Static,
+                                          Mode::PowerMode::MaximumPerformance,
+                                          Mode::PowerMode::PowerSaving});
+
         // restore Power Mode to DBus
         SysPwrMode currentMode;
         uint16_t oemModeData = 0;