s390/hugetlb: Convert PG_arch_1 code to work on folio->flags

Let's make it clearer that we are always working on folio flags and
never page flags of tail pages by converting remaining PG_arch_1 users
that modify page->flags to modify folio->flags instead.

No functional change intended, because we would always have worked with
the head page (where page->flags corresponds to folio->flags) and never
with tail pages.

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20240508182955.358628-11-david@redhat.com


Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>