dt-bindings: usb: dwc3-imx8mp: add power domain property

The USB controllers in the i.MX8MP are located inside the HSIO
power domain. Add the power-domains property to the DT binding
to be able to describe the hardware properly.

Signed-off-by: Lucas Stach <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/usb/fsl,imx8mp-dwc3.yaml

···
     description:
       Power pad (PWR) polarity is active low.
 
+  power-domains:
+    maxItems: 1
+
 # Required child node:
 
 patternProperties:
···
   - clocks
   - clock-names
   - interrupts
+  - power-domains
 
 additionalProperties: false
 
 examples:
   - |
     #include <dt-bindings/clock/imx8mp-clock.h>
+    #include <dt-bindings/power/imx8mp-power.h>
     #include <dt-bindings/interrupt-controller/arm-gic.h>
     usb3_0: usb@32f10100 {
       compatible = "fsl,imx8mp-dwc3";
···
                <&clk IMX8MP_CLK_USB_ROOT>;
       clock-names = "hsio", "suspend";
       interrupts = <GIC_SPI 148 IRQ_TYPE_LEVEL_HIGH>;
+      power-domains = <&hsio_blk_ctrl IMX8MP_HSIOBLK_PD_USB>;
       #address-cells = <1>;
       #size-cells = <1>;
       dma-ranges = <0x40000000 0x40000000 0xc0000000>;