lantiq: dts: Move the &usb_vbus nodes out of &gpio

lantiq: dts: Move the &usb_vbus nodes out of &gpio

Move the USB VBUS regulator nodes out of the GPIO controller node. This
fixes a problem where the "regulator-fixed" driver wasn't probed for
these regulators because the GPIO driver doesn't scan the child-nodes
and based on the dt-bindings documentation it's not supposed to.

This fixed the following error reported by Luca Olivetti:
  ...
  dwc2 1e101000.usb: DWC OTG Controller
  dwc2 1e101000.usb: new USB bus registered, assigned bus number 1
  dwc2 1e101000.usb: irq 62, io mem 0x1e101000
  dwc2 1e101000.usb: startup error -517
  dwc2 1e101000.usb: USB bus 1 deregistered
  dwc2 1e101000.usb: dwc2_hcd_init() FAILED, returning -517

Fixes: FS#1634
Cc: Luca Olivetti <luca@ventoso.org>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>