[Fix firewall work abnormal issue]

[Description]
Fix firewall work abnormal issue
1. add lack kernel config in iptables.cfg
2. reorder kernel config merge order
origin: defconfig->rdkb_cfg->mt7986.cfg
now: defconfig -> mt7986.cfg -> rdkb_cfg

[Release-log]

2 files changed
tree: b116b8a29cc545ef7768891945a48bf3b1c8e34d
  1. classes/
  2. conf/
  3. recipes-connectivity/
  4. recipes-devtools/
  5. recipes-kernel/