[feat] Kindle suspend using lipc (#4825)

Fixes problems with making Kindle go to sleep using menu or gesture manager action.

frontend/device/kindle/powerd.lua

@@ -89,4 +89,10 @@ function KindlePowerD:afterResume()
     end
 end
 
+function KindlePowerD:toggleSuspend()
+    if self.lipc_handle then
+        self.lipc_handle:set_int_property("com.lab126.powerd", "powerButton", 1)
+    end
+end
+
 return KindlePowerD

frontend/ui/uimanager.lua

@@ -1109,7 +1109,7 @@ function UIManager:suspend()
     if Device:isCervantes() or Device:isKobo() or Device:isSDL() or Device:isSonyPRSTUX() then
         self.event_handlers["Suspend"]()
     elseif Device:isKindle() then
-        self.event_handlers["IntoSS"]()
+        Device.powerd:toggleSuspend()
     end
 end