D3D: Fix strided XFB copies

Source/Core/VideoBackends/D3D/FramebufferManager.cpp

@@ -275,8 +275,10 @@ void FramebufferManager::CopyToRealXFB(u32 xfbAddr, u32 fbStride, u32 fbHeight,
                                        const EFBRectangle& sourceRc, float Gamma)
 {
   u8* dst = Memory::GetPointer(xfbAddr);
-  // below div2 due to dx using pixel width
-  s_xfbEncoder.Encode(dst, fbStride / 2, fbHeight, sourceRc, Gamma);
+
+  // The destination stride can differ from the copy region width, in which case the pixels
+  // outside the copy region should not be written to.
+  s_xfbEncoder.Encode(dst, static_cast<u32>(sourceRc.GetWidth()), fbHeight, sourceRc, Gamma);
 }
 
 std::unique_ptr<XFBSourceBase> FramebufferManager::CreateXFBSource(unsigned int target_width,