xhci: fix possible null pointer deref during xhci urb enqueue

xhci: fix possible null pointer deref during xhci urb enqueue

There is a short gap between urb being submitted and actually added to the
endpoint queue (linked). If the device is disconnected during this time
then usb core is not yet aware of the pending urb, and device may be freed
just before xhci_urq_enqueue() continues, dereferencing the freed device.

Freeing the device is protected by the xhci spinlock, so make sure we take
and keep the lock while checking that device exists, dereference it, and
add the urb to the queue.

Remove the unnecessary URB check, usb core checks it before calling
xhci_urb_enqueue()

Suggested-by: Kuen-Han Tsai <khtsai@google.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20231201150647.1307406-20-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>