ethdev: remove experimental tag for iterator API

ethdev: remove experimental tag for iterator API

After removing the function rte_eth_dev_attach(),
there are two replacement solutions possible:
one using probe event notification, and one using a new iterator.
So the application can get the new probed ports either asynchronously
or synchronously.

The iterator API is new in DPDK 18.11 so they got the experimental
tag by policy. It causes an issue for strict applications which do
not use experimental functions, and want to use the synchronous method.

The replacement for removed API should not be experimental.
That's why the experimental status of the ethdev iterator is removed.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Kevin Traynor <ktraynor@redhat.com>
Tested-by: Kevin Traynor <ktraynor@redhat.com>