GPU/HW: Clear depth at vblank time in 480i games

If this is a 480i single buffer game, then rendering should complete within one vblank.
Therefore we should clear the depth buffer, because the drawing area may not change.

src/core/gpu.cpp

@@ -1962,6 +1962,7 @@ void GPU::UpdateDisplay(bool submit_frame)
   cmd->interlaced_display_enabled = interlaced;
   cmd->interlaced_display_field = ConvertToBoolUnchecked(interlaced_field);
   cmd->interlaced_display_interleaved = line_skip;
+  cmd->interleaved_480i_mode = m_GPUSTAT.InInterleaved480iMode();
   cmd->display_24bit = m_GPUSTAT.display_area_color_depth_24;
   cmd->display_disabled = IsDisplayDisabled();
   cmd->display_pixel_aspect_ratio = ComputePixelAspectRatio();

src/core/gpu_hw.cpp

@@ -3908,6 +3908,11 @@ void GPU_HW::UpdateDisplay(const GPUBackendUpdateDisplayCommand* cmd)
 
   GPUTextureCache::Compact();
 
+  // If this is a 480i single buffer game, then rendering should complete within one vblank.
+  // Therefore we should clear the depth buffer, because the drawing area may not change.
+  if (m_pgxp_depth_buffer && cmd->interleaved_480i_mode)
+    CopyAndClearDepthBuffer(true);
+
   if (g_gpu_settings.gpu_show_vram)
   {
     if (IsUsingMultisampling())

src/core/gpu_thread_commands.h

@@ -154,10 +154,11 @@ struct GPUBackendUpdateDisplayCommand : public GPUThreadCommand
   bool interlaced_display_enabled : 1;
   bool interlaced_display_field : 1;
   bool interlaced_display_interleaved : 1;
+  bool interleaved_480i_mode : 1;
   bool display_24bit : 1;
   bool display_disabled : 1;
   bool submit_frame : 1;
-  bool : 2;
+  bool : 1;
 
   GPUBackendFramePresentationParameters frame;
 };