USB_DR_MODE_UNKNOWN should be treated as error as it is done in
cdns3_drd_update_mode().

Fixes: 02ffc26d ("usb: cdns3: fix cdns3_core_init_role()")
Signed-off-by: Roger Quadros <rogerq@ti.com>
Link: https://lore.kernel.org/r/20191017075801.8734-1-rogerq@ti.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>