Removes several calls to __set_page_dirty_nobuffers().  Also turn the
PageSwapCache() case into a BUG() as there's no way for a swapcache page
to make it to a filesystem that doesn't use SWP_FS_OPS.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Acked-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Tested-by: Mike Marshall <hubcap@omnibond.com> # orangefs
Tested-by: David Howells <dhowells@redhat.com> # afs