Potentially it is possible that interrupt may fire after transfer timeout.
That may not end up well for the next transfer because interrupt handling
may race with hardware resetting.

This is very unlikely to happen in practice, but anyway let's prevent the
potential problem by enabling interrupt only at the moments when it is
actually necessary to get some interrupt event.
Tested-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDmitry Osipenko <digetx@gmail.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>