usb: dwc3: gadget: Set gadget_max_speed when set ssp_rate

Set the dwc->gadget_max_speed to SuperSpeed Plus if the user sets the
ssp_rate. The udc_set_ssp_rate() is intended for setting the gadget's
speed to SuperSpeed Plus at the specified rate.

Fixes: 072cab8a ("usb: dwc3: gadget: Implement setting of SSP rate")
Cc: <stable@vger.kernel.org>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/0b2732e2f380d9912ee87f39dc82c2139223bad9.1615254129.git.Thinh.Nguyen@synopsys.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/gadget.c

@@ -2523,6 +2523,7 @@ static void dwc3_gadget_set_ssp_rate(struct usb_gadget *g,
 	unsigned long		flags;
 
 	spin_lock_irqsave(&dwc->lock, flags);
+	dwc->gadget_max_speed = USB_SPEED_SUPER_PLUS;
 	dwc->gadget_ssp_rate = rate;
 	spin_unlock_irqrestore(&dwc->lock, flags);
 }