wifi: ath12k: fix undefined behavior with __fls in dp

When max virtual ap interfaces are configured in all the bands
with ACS and hostapd restart is done every 60s,
a crash is observed at random times because of handling the
uninitialized peer fragments with fragment id of packet as 0.

"__fls" would have an undefined behavior if the argument is passed
as "0". Hence, added changes to handle the same.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1

Fixes: d8899132 ("wifi: ath12k: driver for Qualcomm Wi-Fi 7 devices")
Signed-off-by: Harshitha Prem <quic_hprem@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230821130343.29495-3-quic_hprem@quicinc.com

drivers/net/wireless/ath/ath12k/dp_rx.c

@@ -3238,7 +3238,7 @@ static int ath12k_dp_rx_frag_h_mpdu(struct ath12k *ar,
 		goto out_unlock;
 	}
 
-	if (frag_no > __fls(rx_tid->rx_frag_bitmap))
+	if ((!rx_tid->rx_frag_bitmap || frag_no > __fls(rx_tid->rx_frag_bitmap)))
 		__skb_queue_tail(&rx_tid->rx_frags, msdu);
 	else
 		ath12k_dp_rx_h_sort_frags(ab, &rx_tid->rx_frags, msdu);