D3D12 build fix

src/renderer_d3d12.cpp

@@ -1401,9 +1401,8 @@ namespace bgfx { namespace d3d12
 		{
 		}
 
-		void readTexture(TextureHandle _handle, void* _data, uint8_t _mip) BX_OVERRIDE
+		void readTexture(TextureHandle _handle, void* _data) BX_OVERRIDE
 		{
-			_mip;
 			const TextureD3D12& texture = m_textures[_handle.idx];
 
 			D3D12_RESOURCE_DESC desc = texture.m_ptr->GetDesc();