usb: cdns3: Fix Wunused-but-set-variable warning

usb: cdns3: Fix Wunused-but-set-variable warning

drivers/usb/cdns3/ep0.c: In function cdns3_ep0_feature_handle_device:
drivers/usb/cdns3/ep0.c:290:6: warning: variable wIndex set but not used [-Wunused-but-set-variable]
drivers/usb/cdns3/ep0.c:289:6: warning: variable wValue set but not used [-Wunused-but-set-variable]

wIndex is never used, so remove it.
wValue should be use in the switch statement.

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20190903120615.19504-1-yuehaibing@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>