net/mlx5e: Support tagged tunnel over bond

Stacked devices like bond interface may have a VLAN device on top of
them. Detect lag state correctly under this condition, and return the
correct routed net device, according to it the encap header is built.

Fixes: e32ee6c7

 ("net/mlx5e: Support tunnel encap over tagged Ethernet")
Signed-off-by: Eli Britstein <elibr@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>