MAINTAINERS: Change ownership for SGI specific modules.

I have taken a different job.  I am removing myself as maintainer of
GRU.  Dimitri will continue to maintain the SGI GRU driver, changing the
XP/XPC/XPNET maintainer to Cliff Whickman, but leaving behind my
personal email address to answer any questions about the design or
operation of the XP family of drivers.
Signed-off-by: NRobin Holt <holt@sgi.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -7366,7 +7366,6 @@ F:	drivers/net/ethernet/sfc/
 
 SGI GRU DRIVER
 M:	Dimitri Sivanich <sivanich@sgi.com>
-M:	Robin Holt <holt@sgi.com>
 S:	Maintained
 F:	drivers/misc/sgi-gru/
 
@@ -7386,7 +7385,8 @@ S:	Maintained for 2.6.
 F:	Documentation/sgi-visws.txt
 
 SGI XP/XPC/XPNET DRIVER
-M:	Robin Holt <holt@sgi.com>
+M:	Cliff Whickman <cpw@sgi.com>
+M:	Robin Holt <robinmholt@gmail.com>
 S:	Maintained
 F:	drivers/misc/sgi-xp/