Rename completion helpers

We have io_uring_get_sqe() on the submission side, yet the completion
side is named _completion. Rename as follows:

io_uring_get_completion()	io_uring_peek_cqe()
iO_uring_wait_completion()	io_uring_wait_cqe()

This better tells the user what the _get variant does by calling it
_peek instead, and we move to using _cqe() as the postfix instead
of _completion.

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

examples/io_uring-cp.c

@@ -161,12 +161,12 @@ static int copy_file(struct io_uring *ring, off_t insize)
 			struct io_data *data;
 
 			if (!got_comp) {
-				ret = io_uring_wait_completion(ring, &cqe);
+				ret = io_uring_wait_cqe(ring, &cqe);
 				got_comp = 1;
 			} else
-				ret = io_uring_get_completion(ring, &cqe);
+				ret = io_uring_peek_cqe(ring, &cqe);
 			if (ret < 0) {
-				fprintf(stderr, "io_uring_get_completion: %s\n",
+				fprintf(stderr, "io_uring_peek_cqe: %s\n",
 							strerror(-ret));
 				return 1;
 			}