io_uring: cleanup error-handling around io_req_complete

Move common error-handling to io_req_complete, so that various callers
avoid repeating that. Few callers (io_tee, io_splice) require slightly
different handling. These are changed to use __io_req_complete instead.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220422101048.419942-1-joshi.k@samsung.com


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