arm: octeontx: Enable network support in supported boards

Enable the now included network drivers in the currently supported
Marvell Octeon TX & TX2 boards.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Aaron Williams <awilliams@marvell.com>
Cc: Suneel Garapati <sgarapati@marvell.com>
Cc: Chandrakala Chavva <cchavva@marvell.com>