net: phy: marvell10g: add separate structure for 88X3340

The 88X3340 contains 4 cores similar to 88X3310, but there is a
difference: it does not support xaui host mode. Instead the
corresponding MACTYPE means
  rxaui / 5gbase-r / 2500base-x / sgmii without AN

Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>