ARM: dts: sun8i: sina33: enable ACIN power supply subnode

The Sinlinx SinA33 has an AXP223 PMIC and an ACIN connector, thus, we
enable the ACIN power supply in its Device Tree.

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