[][openwrt][app][Fix Coverity defects in the switch utility, Part2]

[Description]
Fix PHY and VLAN related coverity defects

[Release-log]
N/A


Change-Id: I55cd8d4272f4dfec037be5e0337809b874546208
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/9230901
1 file changed