IB/mlx5: Put non zero value in max_ah

We put INT_MAX since this is the max value that can be held.
Though there is no hardware limitation, this is practically
a large enough number so we can use it.

Fixes: e126ba97 ('mlx5: Add driver for Mellanox Connect-IB adapters')
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>