net: dsa: mv88e6xxx: fix VTU methods for 6320 family

The VTU registers of the 6320 family use the 6352 semantics, not 6185.
Fix it.

Fixes: b8fee957 ("net: dsa: mv88e6xxx: add VLAN Get Next support")
Signed-off-by: Marek Behún <kabel@kernel.org>
Cc: <stable@vger.kernel.org> # 5.15.x
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250317173250.28780-2-kabel@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>