usb: cdns3: ep0: fix the test mode set incorrectly

The 'tmode' is ctrl->wIndex, changing it as the real test
mode value for register assignment.

Fixes: 7733f6c3 ("usb: cdns3: Add Cadence USB3 DRD Driver")
Cc: <stable@vger.kernel.org>
Reviewed-by: Jun Li <jun.li@nxp.com>
Reviewed-by: Pawel Laszczak <pawell@cadence.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Link: https://lore.kernel.org/r/20200623030918.8409-2-peter.chen@nxp.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/cdns3/ep0.c

@@ -327,7 +327,8 @@ static int cdns3_ep0_feature_handle_device(struct cdns3_device *priv_dev,
 		if (!set || (tmode & 0xff) != 0)
 			return -EINVAL;
 
-		switch (tmode >> 8) {
+		tmode >>= 8;
+		switch (tmode) {
 		case TEST_J:
 		case TEST_K:
 		case TEST_SE0_NAK: