uboot-imx

dm: usb: Adjust usb command to prepare for driver model

Use 'udev' instead of 'dev' in a few places, reserving 'dev' for driver
model's struct udevice. Also adjust the code in a few minor ways to make
it easier to plumb in driver model.

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