io_uring: remove IORING_CLOSE_FD_AND_FILE_SLOT

This partially reverts a7c41b46

Even though IORING_CLOSE_FD_AND_FILE_SLOT might save cycles for some
users, but it tries to do two things at a time and it's not clear how to
handle errors and what to return in a single result field when one part
fails and another completes well. Kill it for now.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/837c745019b3795941eee4fcfd7de697886d645b.1655224415.git.asml.silence@gmail.com


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