tipc: Add Ying Xue to TIPC maintainers list

We remove Allan Stephens, who has moved on to other tasks, from
the TIPC maintainers list. He is replaced by Ying Xue, who has
been doing the maintenance on behalf of WindRiver since almost
three years.

Acked-by: Ying Xue <ying.xue@windriver.com>
Acked-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>