ARM: mvebu: update Ethernet compatible string for Armada XP

This patch updates the Ethernet DT nodes for Armada XP SoCs with the
compatible string "marvell,armada-xp-neta".

Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Fixes: 77916519 ("arm: mvebu: Armada XP MV78230 has only three Ethernet interfaces")
Cc: <stable@vger.kernel.org> # v3.8+
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>