net/mlx5: fix link state on device start

net/mlx5: fix link state on device start

Following commit c7bf62255edf ("net/mlx5: fix handling link status event")
the link state must be up in order for the burst function to be set on
the device ops.

As the link may take time to move between down and up state it is
possible the rte_eth_dev_start call will return with wrong burst
function (either null or the empty burst function).

Fixing it by forcing the link to be up before returning from device
start. In case the link is still not up after 5 seconds fail the function.
In addition initialize the burst function on device probe to prevent
crashes before the link is up.

Fixes: c7bf62255edf ("net/mlx5: fix handling link status event")
Cc: stable@dpdk.org
Signed-off-by: Shahaf Shuler <shahafs@mellanox.com>
Acked-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>