X87 FPU state field `dp` is no longer tracked by newer Intel CPUs

The addition of more accurate X87 FPU state tracking revealed an undocumented difference in newer Intel CPUs, that would cause memory-accessing, "non-control" FPU instruction test cases to fail on these newer CPUs:

```gdb
(gdb)  p $native->x87.fxsave64.dp
$1 = 0x0
(gdb)  p $lifted->x87.fxsave64.dp
$2 = 0x18ad970
```

Even slightly older CPUs apparently still track this field.