mm: remove folio_prep_large_rmappable()

mm: remove folio_prep_large_rmappable()

Now that prep_compound_page() initialises folio->_deferred_list,
folio_prep_large_rmappable()'s only purpose is to set the large_rmappable
flag, so inline it into the two callers.  Take the opportunity to convert
the large_rmappable definition from PAGEFLAG to FOLIO_FLAG and remove the
existance of PageTestLargeRmappable and friends.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Miaohe Lin <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Oscar Salvador <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>