io_uring: keep multishot request NAPI timeout current

This refresh statement was originally present in the original patch:
https://lore.kernel.org/netdev/20221121191437.996297-2-shr@devkernel.io/

It has been removed with no explanation in v6:
https://lore.kernel.org/netdev/20230201222254.744422-2-shr@devkernel.io/

It is important to make the refresh for multishot requests, because if no
new requests using the same NAPI device are added to the ring, the entry
will become stale and be removed silently. The unsuspecting user will
not know that their ring had busy polling for only 60 seconds before
being pruned.
Signed-off-by: Olivier Langlois <olivier@trillion01.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Fixes: 8d0c12a8 ("io-uring: add napi busy poll support")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/0fe61a019ec61e5708cd117cb42ed0dab95e1617.1722294646.git.olivier@trillion01.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/poll.c

@@ -347,6 +347,7 @@ static int io_poll_check_events(struct io_kiocb *req, struct io_tw_state *ts)
 		v &= IO_POLL_REF_MASK;
 	} while (atomic_sub_return(v, &req->poll_refs) & IO_POLL_REF_MASK);
 
+	io_napi_add(req);
 	return IOU_POLL_NO_ACTION;
 }