BACKPORT: FROMGIT: mm: Avoid modifying vmf.address in __collapse_huge_page_swapin()

In preparation for const-ifying the anonymous struct field of
'struct vm_fault', rework __collapse_huge_page_swapin() to avoid
continuously updating vmf.address and instead populate a new
'struct vm_fault' on the stack for each page being processed.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will@kernel.org>
Change-Id: Ibabb7b324a2a7debd43e154516c85aaae327b841
Bug: 171278850
(cherry picked from commit 2b635dd3
https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/faultaround

)
[vinmenon: changes for speculative page fault]
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>