net/mlx5e: Add ndo_set_feature for uplink representor

After we have a dedicated uplink representor, the new netdev ops
doesn't support ndo_set_feature. Because of that, we can't change
some features, eg. rxvlan. Now add it back.

In this patch, I also do a cleanup for the features flag handling,
eg. remove duplicate NETIF_F_HW_TC flag setting.

Fixes: aec002f6

 ("net/mlx5e: Uninstantiate esw manager vport netdev on switchdev mode")
Signed-off-by: Chris Mi <chrism@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>