[D3D12] Write to 8_8_8_8_GAMMA in gamma space

src/xenia/gpu/d3d12/shaders/xenos_draw.hlsli

@@ -3,9 +3,9 @@
 
 cbuffer xe_system_cbuffer : register(b0) {
   // vec4 0
+  uint xe_flags;
   uint xe_vertex_index_endian;
   uint xe_vertex_base_index;
-  uint xe_ndc_control;
   uint xe_pixel_pos_reg;
   // vec4 1
   float3 xe_ndc_scale;