net/mlx5: E-Switch, Refactor eswitch SR-IOV interface

Devlink eswitch mode is not necessarily related to SR-IOV, e.g, ECPF
can be at offload mode when SR-IOV is not enabled.

Rename the interface and eswitch mode names to decouple from SR-IOV,
and cleanup eswitch messages accordingly.

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