dt-bindings: pinctrl: sunxi: Make interrupts optional

The R_PIO pinctrl device on the Allwinner H616 SoC does not have an
interrupt (it features only two pins).
However the binding requires at least naming one upstream interrupt,
plus the #interrupt-cells and interrupt-controller properties.

Drop the unconditional requirement for the interrupt properties, and
make them dependent on being not this particular pinctrl device.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20220708105235.3983266-3-andre.przywara@arm.com