dt-bindings: interconnect: sunxi: Add A64 MBUS compatible

A64 contains MBUS controller. Add a compatible for it.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>