net: ethernet: cortina: permit to set mac address in DT

Add ability of setting mac address in DT for cortina ethernet driver.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20220125210811.54350-1-clabbe@baylibre.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>