staging: unisys: Update MAINTAINERS file

Benjamin Romer is no longer a maintainer for the s-Par drivers. David
Kershner will now be the maintainer.
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/unisys/MAINTAINERS

 Unisys s-Par drivers
-M:	Ben Romer <sparmaintainer@unisys.com>
+M:	David Kershner <sparmaintainer@unisys.com>
 S:	Maintained
 F:	Documentation/s-Par/overview.txt
 F:	Documentation/s-Par/proc-entries.txt