Revert "io_uring: support CQE32 for nop operation"

Revert "io_uring: support CQE32 for nop operation"

This reverts commit 7a71875d78b364d8aedf4473fe4bc3999082faca.

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>