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

[ Upstream commit 528876d8 ]

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: 75c05a74

 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>