[][Fix coverity check errors for Eth/HNAT driver]

[Description]
Fix coverity check errors for Eth/HNAT driver.
(145 errors corrected)

[Release-log]
N/A

Change-Id: I1f9839918a6bf93c6af4efb07acb82c89b4d8ea2
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/5264218
9 files changed