net/mlx5: Correctly set LAG mode for ECPF

When bonding is added, driver assumes that it's RoCE LAG if no VF is
enabled. This is not enough for ECPF as the VF is enabled in host PF
side. LAG should only choose RoCE mode when both slave devices meet
conditions below:
 1. E-Switch offloads mode is NONE.
 2. No VF is enabled.

Signed-off-by: Bodong Wang <bodong@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>