net: sched: act_skbedit: remove dependency on rtnl lock

According to the new locking rule, we have to take tcf_lock for both
->init() and ->dump(), as RTNL will be removed.

Use tcf lock to protect skbedit action struct private data from concurrent
modification in init and dump. 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)

Remove rtnl lock assertion that is no longer required.

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