Even though it translates to the same thing down to the binary level, we
should have an array of 2 number cells to describe each voltage state,
which in turns create a validation warning.

Let's fix this.
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/20210114113538.1233933-11-maxime@cerno.tech