mm: Remove PageMappedToDisk

All callers have now been converted to the folio APIs, so remove
the page API for this flag.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://lore.kernel.org/r/20241002040111.1023018-4-willy@infradead.org
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Matthew Wilcox (Oracle)

include/linux/page-flags.h

@@ -554,7 +554,7 @@ FOLIO_FLAG(owner_2, FOLIO_HEAD_PAGE)
  */
 TESTPAGEFLAG(Writeback, writeback, PF_NO_TAIL)
 	TESTSCFLAG(Writeback, writeback, PF_NO_TAIL)
-PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_TAIL)
+FOLIO_FLAG(mappedtodisk, FOLIO_HEAD_PAGE)
 
 /* PG_readahead is only used for reads; PG_reclaim is only for writes */
 PAGEFLAG(Reclaim, reclaim, PF_NO_TAIL)