liquidio: fix wrong information about link modes reported to ethtool

Information reported to ethtool about link modes is wrong for 25G NIC.  Fix
it by checking for presence of 25G NIC, checking the link speed reported by
NIC firmware, and then assigning proper values to the
ethtool_link_ksettings struct.

Signed-off-by: Manish Awasthi <manish.awasthi@cavium.com>
Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>