MAINTAINERS: Add entry for genwqe driver

Frank and I maintain this

Signed-off-by: Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Cc: haver@linux.vnet.ibm.com
Acked-by: Frank Haverkamp <haver@linux.vnet.ibm.com&gt;=>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>