ARM: configs: sunxi: enable Realtek PHY

Lot of sunxi boards has a Realtek PHY, so let's enable it.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Jernej Skrabec <jernej.skrabec@siol.net>
Link: https://lore.kernel.org/r/20201112202652.27676-1-clabbe@baylibre.com