dm: usb: xhci: Use a function to get xhci_ctrl

Rather than getting this directly from struct usb_device, call a function
to obtain it. This will make it possible for driver model to provide it
another way.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marek Vasut <marex@denx.de>
3 files changed