net/mlx4: fix single port configuration

net/mlx4: fix single port configuration

The number of mlx4 present ports is calculated as follows:
conf.ports.present |= (UINT64_C(1) << device_attr.phys_port_cnt) - 1;

That is - all ones sequence (due to -1 subtraction)
When retrieving the number of ports, 1 must be added in order to obtain
the correct number of ports to the power of 2, as follows:
uint32_t ports = rte_log2_u32(conf->ports.present + 1);
If 1 was not added, in the case of one port, the number of ports would
be falsely calculated as 0.

Fixes: 8264279967dc ("net/mlx4: check max number of ports dynamically")
Cc: stable@dpdk.org
Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>