ARM: dts: sun9i: Add mmc controller nodes to the A80 dtsi

The A80 has 4 mmc controllers.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>