[S390] MAINTAINERS: Update zcrypt driver entry

Holger will take over the zcrypt driver maintainer work. Update the
MAINTAINERS entry accordingly.
Signed-off-by: Holger Dengler <hd@linux.vnet.ibm.com>
Signed-off-by: Felix Beck <felix.beck@de.ibm.com>

MAINTAINERS

@@ -5243,8 +5243,7 @@ S:	Supported
 F:	drivers/s390/net/
 
 S390 ZCRYPT DRIVER
-M:	Felix Beck <felix.beck@de.ibm.com>
-M:	Ralph Wuerthner <ralph.wuerthner@de.ibm.com>
+M:	Holger Dengler <hd@linux.vnet.ibm.com>
 M:	linux390@de.ibm.com
 L:	linux-s390@vger.kernel.org
 W:	http://www.ibm.com/developerworks/linux/linux390/