[PATCH STABLE ONLY] add missing page refcount overflow checks

[Vlastimil Babka]

This collection of patches add the missing overflow checks in arch-specific
gup.c variants for x86 and s390. Those were missed in backport of 8fde12ca79af
("mm: prevent get_user_pages() from overflowing page refcount") as mainline
had a single gup.c implementation at that point. See individual patches for
details.

Vlastimil

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2.24.0