s390/virtio: change maintainership

Halil is doing a lot more work in the virtio area on s390 than I
do. Let's reflect the reality in the maintainers file.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

MAINTAINERS

@@ -13324,8 +13324,8 @@ F:	include/uapi/linux/virtio_*.h
 F:	drivers/crypto/virtio/
 
 VIRTIO DRIVERS FOR S390
-M:	Christian Borntraeger <borntraeger@de.ibm.com>
 M:	Cornelia Huck <cornelia.huck@de.ibm.com>
+M:	Halil Pasic <pasic@linux.vnet.ibm.com>
 L:	linux-s390@vger.kernel.org
 L:	virtualization@lists.linux-foundation.org
 L:	kvm@vger.kernel.org