MAINTAINERS: Add myself as maintainer of virtio-vsock

Since I'm actively working on vsock and virtio/vhost transports,
Stefan suggested to help him to maintain it.
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -17212,6 +17212,7 @@ F:	virt/lib/
 
 VIRTIO AND VHOST VSOCK DRIVER
 M:	Stefan Hajnoczi <stefanha@redhat.com>
+M:	Stefano Garzarella <sgarzare@redhat.com>
 L:	kvm@vger.kernel.org
 L:	virtualization@lists.linux-foundation.org
 L:	netdev@vger.kernel.org