[][openwrt][app][Fix Coverity defects in the switch utility, Part4]

[Description]
Fix filtering mac entry related coverity defects

[Release-log]
N/A


Change-Id: I19e16c9cc71a08ab0e69eaa6a9038cbab221805f
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/9230903
1 file changed