MAINTAINERS: update DCO info

Drop the URL for DCO (URL is invalid). Also, point to SubmittingPatches
for the current DCO.

Signed-off-by: Randy Dunlap <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

MAINTAINERS

···
 	or does something very odd once a month document it.
 
 	PLEASE remember that submissions must be made under the terms
-	of the OSDL certificate of contribution
-	(http://www.osdl.org/newsroom/press_releases/2004/2004_05_24_dco.html)
-	and should include a Signed-off-by: line.
+	of the OSDL certificate of contribution and should include a
+	Signed-off-by: line.  The current version of this "Developer's
+	Certificate of Origin" (DCO) is listed in the file
+	Documentation/SubmittingPatches.
 
 6.	Make sure you have the right to send any changes you make. If you
 	do changes at work you may find your employer owns the patch