The comment is correct, but the code ends up moving the bits four
places too far, into the VTUOp field.

Fixes: 11ea809f (net: dsa: mv88e6xxx: support 256 databases)
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>