net: phy: marvell-88q2xxx: add driver for the Marvell 88Q2110 PHY

Add a driver for the Marvell 88Q2110. This driver allows to detect the
link, switch between 100BASE-T1 and 1000BASE-T1 and switch between
master and slave mode. Autonegotiation supported by the PHY does not yet
work.

Signed-off-by: Stefan Eichenberger <eichest@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>