Revert "io_uring: support CQE32 for nop operation"

Revert "io_uring: support CQE32 for nop operation"

This reverts commit bb3146603f17dbc8b26d795333875b72ba1f71c5.

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>