usb: gadget: Introduce udc_set_ssp_rate() for SSP

A SuperSpeed Plus device may operate at different speed and lane count
(i.e. gen2x2, gen1x2, or gen2x1). Introduce gadget ops
udc_set_ssp_rate() to set the desire corresponding usb_ssp_rate for
SuperSpeed Plus capable devices.

If the USB device supports different speeds at SuperSpeed Plus, set the
device to operate with the maximum number of lanes and speed.

Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/9b85357cdadc02e3f0d653fd05f89eb46af836e1.1610592135.git.Thinh.Nguyen@synopsys.com


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