io_uring: remove check_cq checking from hot paths

All ctx->check_cq events are slow path, don't test every single flag one
by one in the hot path, but add a common guarding if.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/dff026585cea7ff3a172a7c83894a3b0111bbf6a.1655310733.git.asml.silence@gmail.com


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