dt-bindings: pinctrl: sunxi: allow vcc-pi-supply

The Allwinner H616 SoC contains a VCC_PI pin, which supplies the voltage
for GPIO port I.
Extend the range of supply port names to include vcc-pi-supply to cover
that.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-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/20220708105235.3983266-5-andre.przywara@arm.com