mm/lru: Add folio LRU functions

Handle arbitrary-order folios being added to the LRU.  By definition,
all pages being added to the LRU were already head or base pages, but
call page_folio() on them anyway to get the type right and avoid the
buried calls to compound_head().

Saves 783 bytes of kernel text; no functions grow.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>