GPU/HW: Fix red bleeding when writing VRAM with mask bit set

Fixes menu screen in Twisted Metal 4.

src/core/gpu_hw_d3d11.cpp

@@ -731,7 +731,7 @@ void GPU_HW_D3D11::UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void* d
                                      width,
                                      height,
                                      map_result.index_aligned,
-                                     m_GPUSTAT.set_mask_while_drawing ? 0xFFu : 0x00,
+                                     m_GPUSTAT.set_mask_while_drawing ? 0x8000u : 0x00,
                                      GetCurrentNormalizedBatchVertexDepthID()};
   m_context->OMSetDepthStencilState(
     m_GPUSTAT.check_mask_before_draw ? m_depth_test_less_state.Get() : m_depth_test_always_state.Get(), 0);

src/core/gpu_hw_opengl.cpp

@@ -782,7 +782,7 @@ void GPU_HW_OpenGL::UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void*
                                        width,
                                        height,
                                        map_result.index_aligned,
-                                       m_GPUSTAT.set_mask_while_drawing ? 0xFFu : 0x00,
+                                       m_GPUSTAT.set_mask_while_drawing ? 0x8000u : 0x00,
                                        GetCurrentNormalizedBatchVertexDepthID()};
     UploadUniformBuffer(&uniforms, sizeof(uniforms));