MAINTAINERS: dccp: move Gerrit Renker to CREDITS

As far as I can tell we haven't heard from Gerrit for roughly
5 years now. DCCP patch would really benefit from some review.
Gerrit was the last maintainer so mark this entry as orphaned.

Subsystem DCCP PROTOCOL
  Changes 38 / 166 (22%)
  (No activity)
  Top reviewers:
    [6]: kstewart@linuxfoundation.org
    [6]: allison@lohutok.net
    [5]: edumazet@google.com
  INACTIVE MAINTAINER Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

CREDITS

@@ -1288,6 +1288,10 @@ D: Major kbuild rework during the 2.5 cycle
 D: ISDN Maintainer
 S: USA
 
+N: Gerrit Renker
+E: gerrit@erg.abdn.ac.uk
+D: DCCP protocol support.
+
 N: Philip Gladstone
 E: philip@gladstonefamily.net
 D: Kernel / timekeeping stuff

MAINTAINERS

@@ -4920,9 +4920,8 @@ F:	Documentation/scsi/dc395x.rst
 F:	drivers/scsi/dc395x.*
 
 DCCP PROTOCOL
-M:	Gerrit Renker <gerrit@erg.abdn.ac.uk>
 L:	dccp@vger.kernel.org
-S:	Maintained
+S:	Orphan
 W:	http://www.linuxfoundation.org/collaborate/workgroups/networking/dccp
 F:	include/linux/dccp.h
 F:	include/linux/tfrc.h