ethdev: add lock to port allocation check

ethdev: add lock to port allocation check

When comparing the port name, there can be a race condition with
a thread allocating a new port and writing the name at the same time.
It can lead to match with a partial name by error.

The check of the port is now considered as a critical section
protected with locks.

This fix will be even more required for multi-process when the
port availability will rely only on the name, in a following patch.

Fixes: 84934303a17c ("ethdev: synchronize port allocation")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>