net/mlx5: close tools socket with last device

net/mlx5: close tools socket with last device

MLX5 PMD exposes a socket for external tools to dump port state.
Socket events are listened using an interrupt source of EXT type.
The socket was closed and the interrupt callback was unregistered
at program exit, which is incorrect because DPDK could be already
shut down at this point. Move actions performed at program exit
to the moment the last MLX5 port is closed. The socket will be opened
again if later a new MLX5 device is plugged in and probed.
Also fix comments that were decisively talking
about secondary processes instead of external tools.

Fixes: e6cdc54cc0ef ("net/mlx5: add socket server for external tools")
Cc: stable@dpdk.org
Reported-by: Harman Kalra <hkalra@marvell.com>
Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>