tipc: Cleanup tipc_nl_bearer_add() error paths

Consolidate the error paths of tipc_nl_bearer_add() under the common label
if the function holds rtnl_lock.

Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Reviewed-by: Tung Nguyen <tung.q.nguyen@dektech.com.au>
Link: https://lore.kernel.org/r/20240213134058.386123-1-syoshida@redhat.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>