ARM: dts: sun5i: Remove SoC node unit-name to avoid warnings

Our main node for all the in-SoC controllers used to have a unit name. The
unit-name, in addition to being actually false, would not match any reg
property, which generates a warning.

Remove it in order to remove those warnings.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>