arm: dts: zynq-zed-adv7511-ad4020: Update to dt doc

During the upstreaming of the AD4000 series driver, the driver file was
renamed from ad400x to ad4000 and the voltage regulator for the ADC
reference was renamed from vref-supply to ref-supply. Update dt to use the
regulator name defined in the device tree documentation and expected by the
new driver.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>

Author: machschmitt

arch/arm/boot/dts/zynq-zed-adv7511-ad4020.dts

@@ -86,7 +86,7 @@
 			spi-max-frequency = <80000000>;
 			vdd-supply = <&adc_vdd>;
 			vio-supply = <&adc_vio>;
-			vref-supply = <&adc_vref>;
+			ref-supply = <&adc_vref>;
 			dmas = <&rx_dma 0>;
 			dma-names = "rx";
 			clocks = <&spi_clk>;