[][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
diff --git a/feed/atenl/files/iwpriv.sh b/feed/atenl/files/iwpriv.sh
index a9b7fcc..fd25212 100755
--- a/feed/atenl/files/iwpriv.sh
+++ b/feed/atenl/files/iwpriv.sh
@@ -251,7 +251,7 @@
 
 function convert_tx_mode() {
     # Remove leading zeros
-    local tx_mode=$(echo $1 | sed 's/^0*//')
+    local tx_mode=$(echo $1 | sed -r 's/0+([0-9]+)/\1/g')
 
     if [ "$tx_mode" = "0" ]; then
         echo "cck"