[][kernel][common][hnat][Fix Coverity scan warning]

[Description]
Fix Coverity scan warning.

[Release-log]
N/A


Change-Id: Iafa443df041c656079bb17dc4706159fcc9cdce6
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6838293
4 files changed