io_uring: remove extra ifs around io_commit_cqring

Now io_commit_cqring() is simple and it tolerates well being called
without a new CQE filled, so kill a bunch of not needed anymore
guards.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/36aed692dff402bba00a444a63a9cd2e97a340ea.1647897811.git.asml.silence@gmail.com


[axboe: fold in followup fix]
Signed-off-by: Jens Axboe <axboe@kernel.dk>