wifi: ath12k: Add memset and update default rate value in wmi tx completion

wifi: ath12k: Add memset and update default rate value in wmi tx completion

When both AP/STA and monitor interfaces are enabled, ieee80211_tx_status()
is invoked from two paths: the TX completion handler for data frames
and the WMI TX completion handler for management frames.
In the data path, the skb->cb is properly zeroed using memset, but in
the WMI path, this step is missing.

As a result, mac80211 encountered uninitialized (junk) values in
skb->cb when generating the radiotap header for monitor mode, leading
to invalid radiotap lengths.

Hence, explicitly zero the status field in the skb->cb using memset
in WMI TX completion path to ensure consistent and correct behavior
during WMI tx completion path.

Additionally, set info->status.rates[0].idx = -1 to indicate that
no valid rate information is available, avoiding misinterpretation of
garbage values.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.4.1-00199-QCAHKSWPL_SILICONZ-1

Signed-off-by: Sarika Sharma <quic_sarishar@quicinc.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/20250603063512.1887652-1-quic_sarishar@quicinc.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>