[][MAC80211][mt76][Fix mt7915 testmode crash in cck modulation]

[Description]
Fix mt7915 testmode crash in cck modulation
Fix iwpriv wrapper ATETXMODE=0 not working due to removing leading zeros
inappropriately

[Release-log]
N/A

Change-Id: I58390e7405b650cb45279bf66dc5ce477c3ac3f6
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7074077
2 files changed