usb: dwc3: dwc3-generic: check the parent nodes

usb: dwc3: dwc3-generic: check the parent nodes

The kernel devicetree has definitions for port and hub nodes as subnodes
to the USB devices. These subnodes don't contain all of the data required
to properly configure the dwc3. Check the parent nodes if the data is not
in the port/hub node.

Here's an example from the librem5 kernel dts file

&usb_dwc3_0 {
	#address-cells = <1>;
	#size-cells = <0>;
	dr_mode = "otg";
	snps,dis_u3_susphy_quirk;
	status = "okay";

	port@0 {
		reg = <0>;

		typec_hs: endpoint {
			remote-endpoint = <&usb_con_hs>;
		};
	};

	port@1 {
		reg = <1>;

		typec_ss: endpoint {
			remote-endpoint = <&usb_con_ss>;
		};
	};
};

&usb_dwc3_1 {
	dr_mode = "host";
	status = "okay";
	#address-cells = <1>;
	#size-cells = <0>;

	/* Microchip USB2642 */
	hub@1 {
		compatible = "usb424,2640";
		reg = <1>;
		#address-cells = <1>;
		#size-cells = <0>;

		mass-storage@1 {
			compatible = "usb424,4041";
			reg = <1>;
		};
	};
};

Signed-off-by: Angus Ainslie <angus@akkea.ca>