usb: cdns3: core: get role switch node from firmware

After that, the role switch device (eg, Type-C device) could call
cdns3_role_set to finish the role switch.

Signed-off-by: Peter Chen <peter.chen@nxp.com>
Reviewed-by: Roger Quadros <rogerq@ti.com>
Link: https://lore.kernel.org/r/20200331081005.32752-1-peter.chen@nxp.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>