net: phy: marvell: Errata for mv88e6390 internal PHYs

[ Upstream commit 8cbcdc1a51999ca81db2956608b917aacd28d837 ]

The VOD can be out of spec, unless some magic value is poked into an
undocumented register in an undocumented page.

Fixes: e4cf8a38 ("net: phy: Marvell: Add mv88e6390 internal PHY")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>