[GPU] Safer and more correct depth bias conversion

Float24-as-float32 depth bias is now in the increments of 8, because conversion of the depth to float24 directly in the pixel shaders may destroy the bias qualitatively otherwise if it's too small.

src/xenia/gpu/d3d12/pipeline_cache.cc

@@ -1435,16 +1435,8 @@ bool PipelineCache::GetCurrentStateDescription(
     float polygon_offset, polygon_offset_scale;
     draw_util::GetPreferredFacePolygonOffset(
         regs, primitive_polygonal, polygon_offset_scale, polygon_offset);
-    float polygon_offset_host_scale = draw_util::GetD3D10PolygonOffsetFactor(
-        regs.Get<reg::RB_DEPTH_INFO>().depth_format, true);
-    // Using ceil here just in case a game wants the offset but passes a value
-    // that is too small - it's better to apply more offset than to make depth
-    // fighting worse or to disable the offset completely (Direct3D 12 takes an
-    // integer value).
-    description_out.depth_bias =
-        int32_t(
-            std::ceil(std::abs(polygon_offset * polygon_offset_host_scale))) *
-        (polygon_offset < 0.0f ? -1 : 1);
+    description_out.depth_bias = draw_util::GetD3D10IntegerPolygonOffset(
+        regs.Get<reg::RB_DEPTH_INFO>().depth_format, polygon_offset);
     description_out.depth_bias_slope_scaled =
         polygon_offset_scale * xenos::kPolygonOffsetScaleSubpixelUnit;
   }