drivers/phy: Add Marvell SerDes / PHY drivers used on Armada 7K/8K

This version is based on the Marvell U-Boot version with this patch
applied as latest patch:

Git ID 7f408573: "fix: comphy: cp110: add comphy initialization for usb
device mode" from 2016-07-05.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Nadav Haklai <nadavh@marvell.com>
Cc: Neta Zur Hershkovits <neta@marvell.com>
Cc: Kostya Porotchkin <kostap@marvell.com>
Cc: Omri Itach <omrii@marvell.com>
Cc: Igal Liberman <igall@marvell.com>
Cc: Haim Boot <hayim@marvell.com>
Cc: Hanna Hawa <hannah@marvell.com>