Make firmware updating more foolproof (#469)

* Make firmware updating more foolproof and fix bugs
* No need to manually handle overflow
* Make startTime TickType_t
* Don't process TouchEvents::None
* Fix sleep getting re-enabled issue more directly

src/displayapp/screens/FirmwareUpdate.h

@@ -2,6 +2,7 @@
 
 #include "Screen.h"
 #include <lvgl/src/lv_core/lv_obj.h>
+#include "FreeRTOS.h"
 
 namespace Pinetime {
   namespace Controllers {
@@ -25,13 +26,17 @@ namespace Pinetime {
         lv_obj_t* titleLabel;
         mutable char percentStr[10];
 
-        States state;
+        States state = States::Idle;
 
-        bool DisplayProgression() const;
+        void DisplayProgression() const;
+
+        bool OnButtonPushed() override;
 
         void UpdateValidated();
 
         void UpdateError();
+
+        TickType_t startTime;
       };
     }
   }