net: dsa: mv88e6xxx: Fix out-of-bound access

If an ATU violation was caused by a CPU Load operation, the SPID could
be larger than DSA_MAX_PORTS (the size of mv88e6xxx_chip.ports[] array).

Fixes: 75c05a7 ("net: dsa: mv88e6xxx: Fix counting of ATU violations")
Signed-off-by: Joseph Huang <Joseph.Huang@garmin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20240819235251.1331763-1-Joseph.Huang@garmin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Joseph Huang

drivers/net/dsa/mv88e6xxx/global1_atu.c

@@ -457,7 +457,8 @@ static irqreturn_t mv88e6xxx_g1_atu_prob_irq_thread_fn(int irq, void *dev_id)
 		trace_mv88e6xxx_atu_full_violation(chip->dev, spid,
 						   entry.portvec, entry.mac,
 						   fid);
-		chip->ports[spid].atu_full_violation++;
+		if (spid < ARRAY_SIZE(chip->ports))
+			chip->ports[spid].atu_full_violation++;
 	}
 
 	return IRQ_HANDLED;