tipc: add reference counter to bearer

[ Upstream commit 2a7ee696f7b000a970dcce0cb06fdcd0a9e6ee76 ]

As a need to support the crypto asynchronous operations in the later
commits, apart from the current RCU mechanism for bearer pointer, we
add a 'refcnt' to the bearer object as well.

So, a bearer can be hold via 'tipc_bearer_hold()' without being freed
even though the bearer or interface can be disabled in the meanwhile.
If that happens, the bearer will be released then when the crypto
operation is completed and 'tipc_bearer_put()' is called.

Acked-by: Ying Xue <ying.xue@windreiver.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Tuong Lien <tuong.t.lien@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 6a2fa13312e5 ("tipc: Fix use-after-free of kernel socket in cleanup_bearer().")
Signed-off-by: Sasha Levin <sashal@kernel.org>