usb: cdns3: ep0: add spinlock for cdns3_check_new_setup

The other thread may access other endpoints when the cdns3_check_new_setup
is handling, add spinlock to protect it.

Fixes: 7733f6c3

 ("usb: cdns3: Add Cadence USB3 DRD Driver")
Cc: <stable@vger.kernel.org>
Reviewed-by: Pawel Laszczak <pawell@cadence.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Link: https://lore.kernel.org/r/20200623030918.8409-4-peter.chen@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>