net_sched: act_mpls: use RCU in tcf_mpls_dump()

Also storing tcf_action into struct tcf_mpls_params
makes sure there is no discrepancy in tcf_mpls_act().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250709090204.797558-8-edumazet@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>