mm: swap-token: fix dead link

http://www.cs.wm.edu/~sjiang/token.pdf is now dead.  Replace it with an
alive alternative.

Signed-off-by: KOSAKI Motohiro <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
1 file changed