liburing.h: add io_uring_prep_cancel_fd()
liburing.h: add io_uring_prep_cancel_fd()

This sets up the cancelation request to be fd based.

Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

axboe/liburing,axboe/liburing,axboe/liburing