Copy usb_otg_descriptor from config's descriptor if host requests
USB_DT_OTG.
Signed-off-by: Macpaul Lin <macpaul@gmail.com> Signed-off-by: Li Jun <jun.li@freescale.com> Reviewed-by: Roger Quadros <rogerq@ti.com> Signed-off-by: Felipe Balbi <balbi@ti.com>