Use tcf spinlock and rcu to protect params pointer from concurrent
modification during dump and init. Use rcu swap operation to reassign
params pointer under protection of tcf lock. (old params value is not used
by init, so there is no need of standalone rcu dereference step)

Ife action has meta-actions that are compiled as standalone modules. Rtnl
mutex must be released while loading a kernel module. In order to support
execution without rtnl mutex, propagate 'rtnl_held' argument to meta action
loading functions. When requesting meta action module, conditionally
release rtnl lock depending on 'rtnl_held' argument.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>