We do not depend on VFS's '->write_super()' anymore and do not need
the 's_dirt' flag anymore, so weed out 'ext4_write_super()' and
's_dirt'.
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: NJan Kara <jack@suse.cz>