[][openwrt][mt7988][hnat][Change header guard in hnat.h]

[Description]
Change header guard in hnat.h

[Release-log]
N/A

Change-Id: I86b717fa14d79b47ce18f1a71ad1648b85defc69
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/9119756
1 file changed