[PATCH net v2] net: dlink: fix multicast stats being counted incorrectly

`McstFramesRcvdOk` counts the number of received multicast packets, and
it reports the value correctly.

However, reading `McstFramesRcvdOk` clears the register to zero. As a
result, the driver was reporting only the packets since the last read,
instead of the accumulated total.

Fix this by updating the multicast statistics accumulatively instaed of
instantaneously.

Fixes: 3401299a1b9e747cbf7de2cc0c8f6376c3cbe565 ("de6*/dl2k/sundance: Move the D-Link drivers")
Tested-on: D-Link DGE-550T Rev-A3
Signed-off-by: Yeounsu Moon <redacted>
---
Changelog:
v1: https://lore.kernel.org/netdev/20250821114254.3384-1-yyyynoom@gmail.com/ (local)
v2:
- Change subject `net-next` to `net`.
- Add `Fixes:` tag.
---
 drivers/net/ethernet/dlink/dl2k.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/dlink/dl2k.c b/drivers/net/ethernet/dlink/dl2k.c
index cc60ee454bf9..6bbf6e5584e5 100644
--- a/drivers/net/ethernet/dlink/dl2k.c
+++ b/drivers/net/ethernet/dlink/dl2k.c

@@ -1099,7 +1099,7 @@ get_stats (struct net_device *dev)
 	dev->stats.rx_bytes += dr32(OctetRcvOk);
 	dev->stats.tx_bytes += dr32(OctetXmtOk);
 
-	dev->stats.multicast = dr32(McstFramesRcvdOk);
+	dev->stats.multicast += dr32(McstFramesRcvdOk);
 	dev->stats.collisions += dr32(SingleColFrames)
 			     +  dr32(MultiColFrames);
 

-- 
2.50.1