Revert "io_uring: support CQE32 for nop operation"

This reverts commit 2bb04df7.

CQE32 nops were used for debugging and benchmarking but it doesn't
target any real use case. Revert it, we can return it back if someone
finds a good way to use it.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/5ff623d84ccb4b3f3b92a3ea41cdcfa612f3d96f.1655224415.git.asml.silence@gmail.com


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