tipc: remove filter and timeout elements from struct tipc_subscription

Until now, struct tipc_subscription has duplicate timeout and filter
attributes present:
1. directly as members of struct tipc_subscription
2. in struct tipc_subscr, which is contained in struct tipc_event

In this commit, we remove the references to these elements as
members of struct tipc_subscription and replace them with elements
from struct tipc_subscr.

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