man/io_uring_enter: mention that SQE entries are always fully consumed
man/io_uring_enter: mention that SQE entries are always fully consumed

With a recent change to the kernel side, we now fully guarantee that
once io_uring_enter(2) returns that X entries have been submitted, it's
completely safe to reuse tohse entries. This used to not always be the
case, if an SQE had to be punted to async context for submission.

This makes for a more reliable and nicer interface.

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

axboe/liburing,axboe/liburing,axboe/liburing