Implement VMNMX shader instruction (#1032)

* Implement VMNMX shader instruction

* No need for the gap on the enum

* Fix typo

Ryujinx.Graphics.Shader/Decoders/VideoType.cs

@@ -0,0 +1,15 @@
+namespace Ryujinx.Graphics.Shader.Decoders
+{
+    enum VideoType
+    {
+        U8  = 0,
+        U16 = 1,
+        U32 = 2,
+
+        Signed = 1 << 2,
+
+        S8  = Signed | U8,
+        S16 = Signed | U16,
+        S32 = Signed | U32
+    }
+}