Print the folio index instead of the pointer, since this is more
useful.  We also don't need to use page_file_mapping() as we do not
invalidate swapcache pages.  Since this is the only caller of
nfs_wb_page_cancel(), convert it to nfs_wb_folio_cancel().
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: NDamien Le Moal <damien.lemoal@opensource.wdc.com>
Acked-by: NDamien Le Moal <damien.lemoal@opensource.wdc.com>
Tested-by: Mike Marshall <hubcap@omnibond.com> # orangefs
Tested-by: David Howells <dhowells@redhat.com> # afs