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.

Cc: <stable@vger.kernel.org>
Fixes: 7733f6c3 ("usb: cdns3: Add Cadence USB3 DRD Driver")
Reviewed-by: Pawel Laszczak <pawell@cadence.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>