tipc: simplify small window members' sorting algorithm

We simplify the sorting algorithm in tipc_update_member(). We also make
the remaining conditional call to this function unconditional, since the
same condition now is tested for inside the said function.

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