Refactor SVC handler (#540)

* Refactor SVC handler

* Get rid of KernelErr

* Split kernel code files into multiple folders

Ryujinx.HLE/HOS/Kernel/SupervisorCall/InvalidSvcException.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace Ryujinx.HLE.HOS.Kernel.SupervisorCall
+{
+    public class InvalidSvcException : Exception
+    {
+        public InvalidSvcException(string message) : base(message) { }
+    }
+}