phy: add the mvebu cp110 comphy driver

On the CP110 unit, which can be found on various Marvell platforms such
as the 7k and 8k (currently), a comphy (common PHYs) hardware block can
be found. This block provides a number of PHYs which can be used in
various modes by other controllers (network, SATA ...). These common
PHYs must be configured for the controllers using them to work correctly
either at boot time, or when the system runs to switch the mode used.
This patch adds a driver for this comphy hardware block, providing
callbacks for the its PHYs so that consumers can configure the modes
used.

As of this commit, two modes are supported by the comphy driver: sgmii
and 10gkr.

Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>