tipc: remove remnants of old broadcast code

We remove a couple of leftover fields in struct tipc_bearer. Those
were used by the old broadcast implementation, and are not needed
any longer. There is no functional changes in this commit.

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>