ARM: dts: sun6i: primo81: Remove useless io-channel-cells

The mma8452 binding doesn't expect an io-channel-cells property, let's
remove it.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Jernej Skrabec <jernej.skrabec@siol.net>
Link: https://lore.kernel.org/r/20210114113538.1233933-10-maxime@cerno.tech