When DM_USB_GADGET the platform code for the USB device must be replaced by
calls to a USB device driver.
usb_gadget_initialize() probes the USB device driver.
usb_gadget_release() removes the USB device driver.
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Lukasz Majewski <lukma@denx.de>