Allow DRAM size to be increased from 4GB to 6GB (#2174)

* Allow DRAM size to be increased from 4GB to 6GB

* Add option on the UI

Ryujinx.HLE/HOS/Kernel/Common/MemroySize.cs

@@ -0,0 +1,9 @@
+namespace Ryujinx.HLE.HOS.Kernel.Common
+{
+    enum MemorySize : byte
+    {
+        MemorySize4GB = 0,
+        MemorySize6GB = 1,
+        MemorySize8GB = 2
+    }
+}