octeontx2-pf: ethtool physical link status

Register get_link_ksettings callback to get link status information
from the driver. As virtual function (vf) shares same physical link
same API is used for both the drivers and for loop back drivers
simply returns the fixed values as its does not have physical link.

ethtool eth3
Settings for eth3:
        Supported ports: [ ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Half 1000baseT/Full
                                10000baseKR/Full
                                1000baseX/Full
        Supports auto-negotiation: No
        Supported FEC modes: BaseR RS
        Advertised link modes:  Not reported
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Advertised FEC modes: None

ethtool lbk0
Settings for lbk0:
	Speed: 100000Mb/s
        Duplex: Full

Signed-off-by: Christina Jacob <cjacob@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>