eth: fbnic: Lock the tx_dropped update

Wrap copying of drop stats on TX path from fbd->hw_stats by the
hw_stats_lock. Currently, it is being performed outside the lock and
another thread accessing fbd->hw_stats can lead to inconsistencies.

Fixes: 5f8bd2c ("eth: fbnic: add support for TMI stats")
Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250802024636.679317-3-mohsin.bashr@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Mohsin Bashir

drivers/net/ethernet/meta/fbnic/fbnic_netdev.c

@@ -423,10 +423,12 @@ static void fbnic_get_stats64(struct net_device *dev,
 	tx_dropped = stats->dropped;
 
 	/* Record drops from Tx HW Datapath */
+	spin_lock(&fbd->hw_stats_lock);
 	tx_dropped += fbd->hw_stats.tmi.drop.frames.value +
 		      fbd->hw_stats.tti.cm_drop.frames.value +
 		      fbd->hw_stats.tti.frame_drop.frames.value +
 		      fbd->hw_stats.tti.tbi_drop.frames.value;
+	spin_unlock(&fbd->hw_stats_lock);
 
 	stats64->tx_bytes = tx_bytes;
 	stats64->tx_packets = tx_packets;