The original logic always enables USB_DR_MODE_HOST operation mode in
dwc3_layerscape_bind() in u-boot. Prevent choosing USB_DR_MODE_HOST
operation mode if USB_HOST is not enabled.
Fixes: 2b0b51d0bed ("usb: dwc3: add layerscape support")
Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@foundries.io>