net: dsa: mv88e6xxx: make const read-only array lanes static

Don't populate the const read-only array lanes on the stack, instead make
it static.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>