[][kernel][mt7988][hnat][add L2TP iface flow offload check]

[Description]
Add l2tp interface flow offload check

[Release-log]
N/A

Change-Id: I90a636db0120c908bb53db8adf7093fb568ca174
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7596212
2 files changed