mm/uffd: fix warning without PTE_MARKER_UFFD_WP compiled in

In the Linux kernel, the following vulnerability has been resolved:

mm/uffd: fix warning without PTE_MARKER_UFFD_WP compiled in

When PTE_MARKER_UFFD_WP not configured, it's still possible to reach pte marker code and trigger an warning. Add a few CONFIG_PTE_MARKER_UFFD_WP ifdefs to make sure the code won't be reached when not compiled in.