Add partial support for the BRX shader instruction

Ryujinx.Graphics.Shader/Decoders/OpCodeBranchIndir.cs

@@ -0,0 +1,23 @@
+using Ryujinx.Graphics.Shader.Instructions;
+using System.Collections.Generic;
+
+namespace Ryujinx.Graphics.Shader.Decoders
+{
+    class OpCodeBranchIndir : OpCode
+    {
+        public HashSet<Block> PossibleTargets { get; }
+
+        public Register Ra { get; }
+
+        public int Offset { get; }
+
+        public OpCodeBranchIndir(InstEmitter emitter, ulong address, long opCode) : base(emitter, address, opCode)
+        {
+            PossibleTargets = new HashSet<Block>();
+
+            Ra = new Register(opCode.Extract(8, 8), RegisterType.Gpr);
+
+            Offset = ((int)(opCode >> 20) << 8) >> 8;
+        }
+    }
+}