wifi: ath12k: replenish the RX buffers reaped without a complete MSDU

ath12k_wifi7_dp_rx_process() returns early when none of the buffers reaped from the REO destination ring ends an MSDU, for example when they are all error pushes or continuation buffers whose last part has not arrived yet. The reaped descriptors are then neither posted back to the refill ring nor freed, and their skbs leak, so the refill ring loses those buffers for good.

Replenish the reaped buffers before checking for complete MSDUs, and free the incomplete ones.

Found by code review while debugging RX stalls on WCN7860.

---
WCN7860 runs here with out-of-tree enablement patches. This path did not trigger in about 105 minutes of TCP soak runs on it, so the fix comes from reading the code.

 drivers/net/wireless/ath/ath12k/wifi7/dp_rx.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

index a32c804403e8..abd262d58a97 100644
@@ -801,9 +801,6 @@ int ath12k_wifi7_dp_rx_process(struct ath12k_dp *dp, int ring_id,
 
 	spin_unlock_bh(&srng->lock);
 
-	if (!total_msdu_reaped)
-		goto exit;
-
 	for (device_id = 0; device_id < ATH12K_MAX_DEVICES; device_id++) {
 		if (!num_buffs_reaped[device_id])
 			continue;

@@ -816,6 +813,11 @@ int ath12k_wifi7_dp_rx_process(struct ath12k_dp *dp, int ring_id,
 					    num_buffs_reaped[device_id]);
 	}
 
+	if (!total_msdu_reaped) {
+		__skb_queue_purge(&msdu_list);
+		goto exit;
+	}
+
 	ath12k_wifi7_dp_rx_process_received_packets(dp, napi, &msdu_list,
 						    ring_id);