Improve kernel events implementation (#430)

* Improve kernel events implementation

* Some cleanup

* Address PR feedback

Ryujinx.HLE/HOS/Kernel/KernelResult.cs

@@ -0,0 +1,10 @@
+namespace Ryujinx.HLE.HOS.Kernel
+{
+    enum KernelResult
+    {
+        Success         = 0,
+        HandleTableFull = 0xd201,
+        InvalidHandle   = 0xe401,
+        InvalidState    = 0xfa01
+    }
+}