mm: Add functions to support extra actions on swap in/out

mm: Add functions to support extra actions on swap in/out

If a processor supports special metadata for a page, for example ADI
version tags on SPARC M7, this metadata must be saved when the page is
swapped out. The same metadata must be restored when the page is swapped
back in. This patch adds two new architecture specific functions -
arch_do_swap_page() to be called when a page is swapped in,
arch_unmap_one() to be called when a page is being unmapped for swap
out.

This is a backport of patch sent upstream and brings UEK code in sync
with upstream patch v6.

Orabug: 22713162

Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Khalid Aziz <khalid@gonehiking.org>