BACKPORT: arm64/mm: Convert to using lock_mm_and_find_vma()

commit ae870a68 upstream.

This converts arm64 to use the new page fault helper.  It was very
straightforward, but still needed a fix for the "obvious" conversion I
initially did.  Thanks to Suren for the fix and testing.

Fixed-and-tested-by: Suren Baghdasaryan <surenb@google.com>
Unnecessary-code-removal-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[surenb: this one is taken from 6.4.y stable branch]
Change-Id: Ibda94ca9b3893b8961e1d6536c854c0aee559a6b
(cherry picked from commit ae870a68)
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>