net: Add NIC controller driver for OcteonTX

Adds support for Network Interface controllers found on
OcteonTX SoC platforms.

Signed-off-by: Suneel Garapati <sgarapati@marvell.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Joe Hershberger <joe.hershberger@ni.com>