mlx4: Fix access to freed memory

catas_reset() uses pointer to mlx4_priv, but mlx4_priv is not valid
after call mlx4_restart_one().

Signed-off-by: Vitaliy Gusev <vgusev@openvz.org>
Acked-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>