When ring enters polling mode we are expected to mask the ring interrupt
before the callback is called. However, the current code actually
unmasks it probably because of a copy-paste mistake.

Mask the interrupt properly from now on.

Fixes: 4ffe722e ("thunderbolt: Add polling mode for rings")
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Yehezkel Bernat <yehezkel.bernat@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>