Add missing optional phy-supply property used to power up PHY regulators.

Fixes: 87a55485 ("dt-bindings: phy: meson-g12a-usb3-pcie-phy: convert to yaml")
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230207-b4-amlogic-amlogic-g12a-usb3-pcie-phy-fix-v1-1-3e437b759549@linaro.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>