usb: cdns3: gadget: Fix full-speed mode

We need to disable USB3 PHY for full-speed mode else
gadget mode is broken.
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Link: https://lore.kernel.org/r/20191007121601.25996-3-rogerq@ti.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/cdns3/gadget.c

@@ -2571,6 +2571,7 @@ static int cdns3_gadget_start(struct cdns3 *cdns)
 	switch (max_speed) {
 	case USB_SPEED_FULL:
 		writel(USB_CONF_SFORCE_FS, &priv_dev->regs->usb_conf);
+		writel(USB_CONF_USB3DIS, &priv_dev->regs->usb_conf);
 		break;
 	case USB_SPEED_HIGH:
 		writel(USB_CONF_USB3DIS, &priv_dev->regs->usb_conf);