net/mlx5: Put elements related to offloaded TC rule in one struct

Put the representors related to the source and dest vports and the
action in struct mlx5_esw_flow_attr which is used while setting the FDB rule.

This patch doesn't change any functionality.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>