Termination tables are used for vlan push actions on uplink ports.
To support RoCE dual port the source port value was placed in a register.
Fix the code to use an API method returning the source port according to
the FW capabilities.

Fixes: 10caabda ("net/mlx5e: Use termination table for VLAN push actions")
Signed-off-by: Dmytro Linkin <dmitrolin@mellanox.com>
Reviewed-by: Jianbo Liu <jianbol@mellanox.com>
Reviewed-by: Oz Shlomo <ozsh@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>