The VDD-CPU and VDD-GPU regulators were incorrectly swapped.

Fixes: bab03561 ("ARM: dts: sun6i: hummingbird: Add AXP221 regulator
       nodes")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>