net/mlx5: LAG demux flow table support

Add interfaces to allow the creation and destruction of a
LAG demux flow table.

It is a special flow table used during LAG for redirecting
non user-mode packets from PF0 to PF1 root ft, if a packet was
received on phys port two.

Signed-off-by: Aviv Heller <avivh@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>