cxgb4/cxgb4vf: link management changes for new SFP

newer SFPs like SFP28 and QSFP28 Transceiver Modules present
several new possibilities which we haven't faced before. Fix the
assumptions in the code reflecting the more limited capabilities
of previous Transceiver Module systems

Original work by Casey Leedom <leedom@chelsio.com>

Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>