fixup! mm/gup: handle huge pmd for follow_pmd_mask()

Allow follow_pmd_mask() to take hugetlb tail pages.  The old warnings do
not help now as hugetlb now allows it to happen, so drop them.

Reported-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Peter Xu <peterx@redhat.com>