net/mlx5: Use port_num 1 instead of 0 when delete a RoCE address

In multi-port mode, FW reports syndrome 0x2ea48 (invalid vhca_port_number)
if the port_num is not 1 or 2.

Fixes: 80f09dfc ("net/mlx5: Eswitch, enable RoCE loopback traffic")
Signed-off-by: Mark Zhang <markzhang@nvidia.com>
Reviewed-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>