ARM: dts: sun9i: Enable i2c3 on A80 Optimus board

i2c3 is exposed on the GPIO extension header. Enable it so we can use it.

Also enable internal pull-ups on the pins, as they don't seem to have
external pull-up resistors.

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