ARM: sun7i: a20: cubieboard2: Move usb_otg node for alphabetical ordering

We want to keep node references in alphabetical order, except for
instances where node must be #included first.

Move the usb_otg node reference so that all references to non-AXP209
device nodes are in alphabetical order.

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