net/mlx4: fix crash on info query in secondary process

net/mlx4: fix crash on info query in secondary process

mlx4_dev_info_get calls mlx4_get_ifname, but mlx4_get_ifname
uses priv->ctx which is not a valid pointer in a secondary
process. The fix is to cache the value in primary.

In the primary process, get and store the interface index of
the device so that secondary process can see it.

Bugzilla ID: 320
Fixes: 61cbdd419478 ("net/mlx4: separate device control functions")
Cc: stable@dpdk.org
Reported-by: Suyang Ju <sju@paloaltonetworks.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Matan Azrad <matan@mellanox.com>