maxwell_3d: Use correct const buffer size and check bounds.

- Fixes mem corruption with Super Mario Odyssey and Pokkén Tournament DX.

src/video_core/engines/maxwell_3d.cpp

@@ -238,6 +238,8 @@ void Maxwell3D::ProcessCBBind(Regs::ShaderStage stage) {
 
     auto& buffer = shader.const_buffers[bind_data.index];
 
+    ASSERT(bind_data.index < Regs::MaxConstBuffers);
+
     buffer.enabled = bind_data.valid.Value() != 0;
     buffer.index = bind_data.index;
     buffer.address = regs.const_buffer.BufferAddress();

src/video_core/engines/maxwell_3d.h

@@ -44,7 +44,7 @@ public:
         static constexpr size_t MaxShaderProgram = 6;
         static constexpr size_t MaxShaderStage = 5;
         // Maximum number of const buffers per shader stage.
-        static constexpr size_t MaxConstBuffers = 16;
+        static constexpr size_t MaxConstBuffers = 18;
 
         enum class QueryMode : u32 {
             Write = 0,