kernel: sweep — usb2phy port (USB host up) + saradc data port

usb2phy: ported the RV1106 inno-usb2 phy config to 6.18 (rv1106_usb2phy_cfg;
fields map 1:1 except utmi_iddig->utmi_id and chg_mode->opmode; 5.10-only
iddig_output/en/bvalid_grf_sel dropped; phy_tuning left off, guarded so safe).
With PHY_ROCKCHIP_INNO_USB2=y + the u2phy/usbdrd/dwc3 DT enabled, verified on
warden-c8a3: the DWC3 comes up as xhci-hcd @ 0xffb00000 — USB host works. eth0
gadget just needs dr_mode=peripheral.

saradc: added rv1106_saradc_data (2-ch v2, matches the vendor) + the native
compatible. Driver now matches; probe still returns -22 (a clk-rate/setup detail,
not the data) — TODO.

Also captured: the growing board dts (USB nodes), the port fragments under usb/
and adc/. DRIVER-PARITY.md updated: ~14 drivers now at parity on 6.18.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017wB8KB3MMQztRDXCMCkPrf

kernel/rv1106-enablement/dts/rv1106-warden.dts

@@ -128,3 +128,21 @@
 &rgb {
 	status = "disabled";
 };
+
+/* --- sweep: USB OTG (eth0 gadget / host) via the ported inno-usb2 phy --- */
+&u2phy {
+	status = "okay";
+};
+
+&u2phy_otg {
+	status = "okay";
+};
+
+&usbdrd {
+	status = "okay";
+};
+
+&usbdrd_dwc3 {
+	status = "okay";
+	dr_mode = "otg";
+};