net/mlx5e: IPoIB, Add support for get_link_ksettings in ethtool

Add support for "ethtool DEVNAME" over ipoib ports,
Display standard port information for IPoIB netdevices using ethtool
For example:
$ ethtool ib2
> Settings for ib2:
        Supported ports: [ ]
        Supported link modes:   Not reported
        Supported pause frame use: No
        Supports auto-negotiation: No
        Advertised link modes:  Not reported
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Speed: 100000Mb/s
        Duplex: Full
        Port: Other
        PHYAD: 0
        Transceiver: internal
        Auto-negotiation: off
        Link detected: yes

Signed-off-by: Shalom Lagziel <shaloml@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>