io_uring: fix code style problems

Fix a bunch of problems mostly found by checkpatch.pl

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/cfaf9a2f27b43934144fe9422a916bd327099f44.1624543113.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>