migrate: convert unmap_and_move() to use folios

Patch series "migrate: convert migrate_pages()/unmap_and_move() to use
folios", v2.

The conversion is quite straightforward, just replace the page API to the
corresponding folio API.  migrate_pages() and unmap_and_move() mostly work
with folios (head pages) only.


This patch (of 2):

Quite straightforward, the page functions are converted to corresponding
folio functions.  Same for comments.

Link: https://lkml.kernel.org/r/20221109012348.93849-1-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20221109012348.93849-2-ying.huang@intel.com


Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>