net: fman: Configure fixed link in memac_initialization

memac is the only mac which parses fixed links. Move the
parsing/configuring to its initialization function.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Acked-by: Camelia Groza <camelia.groza@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>