mm, hugetlb: increment the number of pages to be reset on HVO

mm, hugetlb: increment the number of pages to be reset on HVO

commit 4eeec8c89a0c ("mm: move hugetlb specific things in folio to
page[3]") shifted hugetlb specific stuff, and now mapping overlaps
_hugetlb_cgroup field.

Upon restoring the vmemmap for HVO, only the first two tail pages are
reset, and this causes the check in free_tail_page_prepare() to fail as it
finds an unexpected mapping value in some tails.

Increment the number of pages to be reset to 4 (head + 3 tail pages)

Link: https://lkml.kernel.org/r/20250415111859.376302-1-osalvador@suse.de
Fixes: 4eeec8c89a0c ("mm: move hugetlb specific things in folio to page[3]")
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Suggested-by: David Hildenbrand <david@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>