net/mlx5e: Report netdevice MPLS features

Set supported device features in the netdevice MPLS features mask.
This will enable HW checksumming and TSO for MPLS tagged traffic.

Signed-off-by: Ariel Levkovich <lariel@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>