prepo: Implement calls of IPrepoService (#830)

* prepo: Implement calls of IPrepoService

- Implement `SaveReportOld`, `SaveReportWithUserOld`, `SaveReport`, `SaveReportWithUser` not accurate by RE (except for result codes). It's  here to do something with the data since we will never use the `Play Report` sent by the game. So it's better than just a stub.
- Fix a typo in `ldn` result code.

Close #807

* Add a processing method

* Address some comments

* remove unneeded using

* Resolve requested changes

* Typo

* Update IPrepoService.cs

Ryujinx.HLE/HOS/Services/Prepo/ResultCode.cs

@@ -0,0 +1,15 @@
+namespace Ryujinx.HLE.HOS.Services.Prepo
+{
+    enum ResultCode
+    {
+        ModuleId       = 129,
+        ErrorCodeShift = 9,
+
+        Success = 0,
+
+        InvalidArgument   = (1 << ErrorCodeShift) | ModuleId,
+        InvalidState      = (5 << ErrorCodeShift) | ModuleId,
+        InvalidBufferSize = (9 << ErrorCodeShift) | ModuleId,
+        Unknown1          = (90 << ErrorCodeShift) | ModuleId
+    }
+}