__io_uring_get_cqe: don't subtract negative error from 'submit'
__io_uring_get_cqe: don't subtract negative error from 'submit'

Only subtract if we know it's >= 0.

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

axboe/liburing,axboe/liburing,axboe/liburing