Bluetooth: Fix issue with USB suspend in btusb driver

Suspend could fail for some platforms because
btusb_suspend==> btusb_stop_traffic ==> usb_kill_anchored_urbs.

When btusb_bulk_complete returns before system suspend and resubmits
an URB, the system cannot enter suspend state.

Signed-off-by: Champion Chen <champion_chen@realsil.com.cn>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Cc: stable@vger.kernel.org